Chaga Recipes
I searched the internet for information on Chaga tea.  It appears that Russians have been making and drinking Chaga tea for centuries.  It was used as a substitute for real tea by people who could not afford the real thing.  It is hard to believe that they went through an intricate recipe given below.  Most likely they broke the Chaga into small pieces, put it in a tea kettle with water and boiled it until the tea was dark in color.   The first recipe stresses that Chaga should not be boiled.  The sixth recipe says that you have to boil it in order to activate the anti cancer part of the Chaga.  Some say to boil it up to 2 hrs.  This does not seam reasonable since most if not all the water would boil away.  I boil mine about 15 minutes then let it cool overnight. 

#1.  Preparation: The dried, shredded inner part of the conk is softened by soaking in cold but previously boiled water for 4 hours. Filter and save both the liquid portion as well as the softened fungus. An infusion is prepared by pouring sterilized boiled water, cooled to 50º C (122º F), over the fungus (use a weight ratio of about 1:5 fungus to water). Let stand at room temperature for 48 hours. The mixture is then filtered (coffee filter) and the water in which the fungus was originally soaked is added to the filtrate.
Dosage: The infusion can be used for up to 4 days. Three glasses should be taken per 24-hour period,
approximately 30 minutes before meals. It takes some 7 kg a month of the fungus for a course of treatment, lasting 4 to 7 months, with short breaks if necessary.
Note: It is important to never overheat the fungus and to treat it as you would yeast, never subjecting it to too much heat or cold.

The above was the most common recipe found on the Internet.  It appears to be based on the recipe used to make an infusion to treat illnesses in Russia:
After harvesting the Chaga from a living birch, remove the brown part that was growing closest to the tree.  They say use the first three layers next to the tree.  They do not explain how to recognize the layers.  They do say that the most potent part of the Chaga is that which has the white veins running through it.  The consistency of the Chaga is that of hard cork.  I used a wood drill to remove the desired Chaga but it is a messy process and is best done outside.  Also try to do this soon after harvest while the Chaga is relatively soft.  After it dries it becomes much harder to work.  By using a drill you shred it to desired state.  Set it out to dry, then you can store it in air tight containers until needed.  Make sure it is thoroughly dry before putting in air tight containers otherwise molds will form on it and ruin it.
Dry Chaga is very light, like cork.  The 1:5 ratio given above must be for the pre soaked Chaga.  How much water you use in the pre soak stage is not given but I assume it would be minimum to wet the dry Chaga.  If not all the water is soaked up by Chaga in this stage then It is saved.  If the Chaga is dripping wet after 4 hours of soaking I would press it by hand to remove the excess water before weighing it.  So for each ounce of wet Chaga you would add 5 ounces of 122º F water.  The statement The infusion can be used for up to 4 days. Should have said "The infusion should be used up within 4 days."  I appears that the infusion starts to lose its potency after 4 days.  If you are using it to treat a serious medical condition you should have a fresh batch ready for the 5th day.

#2.  This is a variation of recipe #1 that I came up with.  It is something half way between an infusion and a tea.  Right after harvesting remove the black part of the Chaga by using a wood chisel.  Using different size wood chisels enables you to remove the black part with minimum amount of waste of the good brown part.  Bill Neill came up with the good idea of removing the black from the Chaga while it is still on the tree.  He used a wood chisel and hammer.  This way it stays put while you are cleaning it.  After cleaning, cut it up into 1" or thereabout cubes.  These you can put in a dehydrator and dry them at about 105º F.  Put them in an air tight container for storage.  It should keep for years if stored in a cool dry place.  An advantage of using these cubes rather than drill shavings is that you do not have to filter the liquid.  Filters tend to get plugged up quickly when Chaga powder is used to make the infusion.  I use a 2 gallon stainless steel pot to make the infusion.  I fill it with water and bring it to a boil.  Take it off the heat and let it cool until I can touch the pot and not get burned.  Then I take 3 or 4 handfuls of the dry cubes and put them into the water.  Cover the pot with a lid and let it stand 48 hrs or so.  I then strain the liquid into plastic soda bottles and store them in the refrigerator.  The used cubes can be used at least two more times.  The last time I even put them in boiling water and boil them for about 10 minutes.  There is another school of thought that say that the anti cancer ingredients of Chaga are released only when boiled.

#3.  Put 5-10cm pieces of Chaga into a pot and fill it with boiled and cooled water (not more
than 50-60 degrees Celsius ) and infuse for 4 hours.  For medical purposes the mushroom Chaga should be gathered only from live birch and is prepared from the dried, ground Chaga.
Afterwards, the soaked pieces of Chaga should be crushed through mincing machine or grater.  For each 1 part of crushed Chaga add 5 parts of boiled and cooled water (t<60 C) and
infuse for 48 hours at room temperature.  Pour out the liquid into another pot through filter (or through a gauze) and add the liquid left from first infusion.  The decoction can be stored for 4 days in a cool, dark place.  Take three glasses (200g glass = 1 cup= 8oz.) a day minimum, not only against bowel cancer but against other tumors. When having a pelvis minor cancer (prostate cancer, rectum cancer) take an enema with 50-100 ml of warm Chaga decoction
additionally early in the morning and before going to sleep in the evening
TO PREPARE A LIQUEUR
Put three table spoons of milled Chaga into 0,5 liter of vodka and keep it for
two weeks in a cool dark place. Shake from time to time. In two weeks filter
the contents, squeezing the liquid out of the remaining pieces of Chaga.
Dosage: take 3 table spoons of the liquid 3-6 times a day.
IMPORTANT
While taking Chaga beverages do not take penicillin and do not use
intravenous injections of glucose. Those substances are antagonists to Chaga.
The above recipe was obtained from a Russian web site.  I corrected some poor translation into English plus added English measure equivalents.  This recipe is basically the same as #1 but is made from cubes of Chaga instead of ground powder. 

#4  In David Arora's "All That the Rain Promises, and More..." has the following Chaga tea recipe:  Tea prepared from Chaga is widely used by Siberians and Russians ... to enhance the immune system and combat or prevent cancer. To make Chaga tea: cut into pieces with an ax and soak for 6-8 hours, then powder the soaked chunks by running them through a meat grinder. Bring 5 ups of water to a boil and stir in 1 cup of ground Chaga. Steep for an hour or two, then filter and drink, reheating it if desired (excess can be kept in a thermos). The tea is richly colored with a very mild flavor."
It looks like this recipe does not use dry Chaga.  It sounds like they chop the Chaga off the tree and make tea right away.  I am sure you will not ruin the recipe if you use a knife to cut up the Chaga :o)  I do not even use an ax to remove the Chaga from the tree.  My aim with an ax is not that good plus the thing that you chop off tends to fly off into the next county.  I like to use a sharp cleaver and a sturdy cutting board.  I place the cleaver on the piece of Chaga and then press it slowly in. 

#5  This is the recipe that I currently use for Chaga tea.  I think of this as the lazy man's Chaga tea.  After I harvest the Chaga I bring it home and let it lie around till it is good and dry.  I do not clean it.  As it dries it develops cracks and can be more easily broken into smaller pieces.  When I make a batch of tea I again use my 2 gallon pot and boil up some water.  I take it off the heat and drop in a few handfuls of Chaga pieces, black parts and all.  I let it steep at room temperature for 2 days then strain it into bottles and store in the refrigerator.  I like to drink it cold.  Sometimes I drink it straight, other times I will spike it with ginger ale for the change of pace :o)  I use the same Chaga pieces about 4 more times.  The last time I will even boil the Chaga pieces to get a liquid a bit darker.  One Russian recipe I read calls for the boiling of Chaga to bring out its anti cancer properties.  When I find it I will add it to this list.

#6  Chaga has been prepared as a tea, decoction, extract, syrup injection, suppository, tablet and aerosol (Hartwell 1971). Use the inner yellow and golden mass closer to the tree. Prepare a tea by boiling the ingredients for a few minutes. Use approximately 3 square centimeters or one tablespoon of crushed mushroom. It will produce 2.5 - 3 liters of tea to be to be taken in a dose of 3 cups per day, ½ hour before meals. Continue for 15-20 weeks with intervals of 7-10 days.  According to anti-tumour studies, boiling activates anti-tumour particles leading to tumour inhibition in mice (Lucas 1960). So, it seems that both folklore and laboratory evidence point toward boiling the fungus and administering the tea.
This recipe, from a Russian web site, contradicts the others where you are warned not to boil the Chaga.  The Russian peasants that used Chaga for centuries most likely used boiling water to make their tea.  So it appears that you can make the tea anyway you want and still get the benefits of the healing power of Chaga.