I mentioned this in a discussion on another board about dealing with guests' diet requirements - it was something I invented when we were going to host a couple of vegetarians. Luckily, they DID eat dairy!
Noodles in Cream with Mushrooms
1 lb. assorted mushrooms - oyster, Crimini, morels, whatever. Plain old white buttons work.
1 small white or yellow onion
12-16 oz. creme fraiche*
1 Tbs. butter
2-4 Tbs. olive oil
1 lb. fettucini, tagliatelle, or egg noodles
Salt, pepper, Parmesan (optional), green onions (optional)
*Buy at specialty market, or make your own: 1 cup whipping cream, 1 cup sour cream (light works too). Whisk together lightly in a bowl to mix at least two hours before using. Cover bowl loosely and let sit at room temperature for two hours, then pour into pint jar and refrigerate (unless youre going to use it right away). Will keep for about a week.
Clean mushrooms (brush off crud - DO NOT WASH!), then chop coarsely, discarding tough stems. Chop onion fine. Heat oil and butter in deep skillet, then cook onion gently 5-10 minutes until its soft. Remove with a slotted spoon into a bowl, gently pressing oil back into skillet. Add oil or butter if its needed, bring heat to medium-high and sauté mushrooms until theyre tender and beginning to throw off juices. Remove to bowl. Do NOT wipe out skillet.
This is a good time to cook the noodles...
Pour room-temperature creme fraiche into skillet. Use a wooden spoon or stir-fry paddle (nowadays I would use a silicone spatula) to stir, constantly scraping cream from bottom of pan, until it boils. Adjust heat to maintain a middling sort of boil, and continue to scrape and stir. After about five minutes it will begin to thicken noticeably; when its as thick as you want it, reduce the heat, stir in some grated Parmesan if you want it, salt and pepper to taste. Stir the mushrooms and onion back in, and heat to let the flavors blend. When the noodles are done, drain them and stir into the sauce. Let sit in a warm place, covered, while you set the table (or about ten minutes). Pour into a serving dish - theyre OK from the skillet, but this puts the settled cream sauce back on top - and garnish with chopped scallions (both white and green) if you want to.
I'd just like to add that this was one of a series of explorations I did on the cream-reduction theme, all of which were wickedly good. Wonderful way to make a sauce, if not exactly diet food!