Use the tree part. It grows on WOOD chips, not bark chips. Remember, the bark is designed by the tree to have special medicines in it to stop fungus from taking it over, to protect the wood. You want the wood. Also bark dries out faster=death for fungi.
Thanks John... is there a size limit for the chips? I have access to some chips from the local power company, but the chips might be 1-2 inches. Is that too big? The advantage is that they would be very fresh... as in just cut. and, I would know what kind of wood it is.
That's not a problem. Sticks, like 4-8 inches long and 1-2 inches wide, won't inoculate well, but those chips should be fine. Keep them moist. I would put cardboard down on bare soil first, then spawn, then chips. I would put straw casing on top to keep moisture in and sun out.
I assume this person got an answer somewhere, but in case someone else wants to know - no, the straw does not need to be sterilized. You can "cold sterilize" by soaking it in water (look for that online for instructions). It washes out anything you need to worry about and also wets the straw, which you need to do anyway. Just don't use rotting straw that may already have fungus in residence. I use burlap bags filled with straw to make it easy to remove and carry. I soak the bags in a plastic garbage can. The burlap releases tannins, but that doesn't hurt anything and you can use the water for watering, assuming that your burlap bags are untreated. I use burlap bags to top the bed. The stropharia love them - it greatly increases my yield.