Our dr crunched it up and put various increments in yogurt - they offered to use yogurt, apple sauce or pudding. Finds it makes it more palatable. He had increasing doses in spoonfuls of yogurt until he passed.
Now our allergist was pretty confidant that tree nuts and peanuts were a false positive. We did one nut first (almonds, I think) and then did three nuts combined three times to finish them off. Then peanuts were a separate challenge. Five separate challenges in five weeks. I missed the peanut challenge because I had the flu. DH took him and he is not the umm, comforting sort but more of the man up and do it kind of person. DS1 hated the four nut challenges because they tasted like poo to him (he is still not a fan of tree nuts) and the peanut apparently began with the ultimate fun - DS refused to come out from under the chair. It's funny now, but I am pretty lucky DH didn't have an aneurysm over it.