Adapted from Nika Hazelton's "Way with Vegetables".
For a lighter version, you can substitute half-and-half for heavy cream, though the sauce will be less rich.
Any variety of mushroom works well, but cremini or button mushrooms are traditional.
Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. Reheat gently on the stove.