This is an adaptation of a very basic soufflé recipe. I think this one originally derived from The Joy of Cooking, but with my fungal augmentations. From my experience, the two key elements to success with a soufflé is to start with room temperature eggs, and to fold in the whipped egg whites immediately after whipping. It's really not that hard. This recipe uses Russula xerampolina, but I have also made it with Agaricus silvicola, Agaricus augustus and chantrelles to very good effect.
Start by setting the oven to 325º F to preheat. Assemble together:
Clean and chop the mushrooms. Crush and dice the garlic. Sautée the above ingredients for 5-10 minutes, until the liquid from the mushrooms has boiled away. Remove from heat and start the cream sauce:
Melt the butter in a medium saucepan, stir in the flour and let turn slightly darker after a few minutes heating, then slowly stir in the milk. Do not allow the milk to boil. Remove from heat. Now prepare the following:
Separate the egg yolks from the whites. Beat the 3 egg yolks and stir them into the cream sauce base. Add the parsley, nutmeg, salt and pepper. Now stir in the sautéed mushrooms and set aside. Prepare a 9" souffle bowl by coating the bottom and sides with butter, followed by a dusting of flour.
Now whip the 3 egg whites to a stiff, but not dry, consistency. Immediately after whipping, carefully fold the whipped eggs into the mushroom cream sauce mixture. Pour the result into the soufflée dish and place into the preheated 325º oven for 40 minutes. Serve immediately after removing from the oven.