Combined this with a side salad and the sauce idea from here: Ingredients:

2 pounds of fresh mushrooms
3 tablespoons butter, divided
2 tablespoons chopped parsley leaves
Coarse salt and freshly-ground black pepper to taste
1 tablespoon all-purpose flour
1 egg yolk
Juice of 1 lemon

Preparation:

Using a brush and a damp sponge, clean the mushrooms; trim and slice the mushrooms lengthwise.

In a large frying pan over medium-high heat, melt 2 tablespoon butter; add mushrooms and saute for 5 minutes, stirring frequently. Sprinkle parsley over the mushrooms and season with salt and pepper. Reduce heat to low.

In a separate saucepan, melt the remaining 1 tablespoon butter; stir in flour, egg yolk, and lemon juice until combined. Pour the lemon sauce over the cooked mushrooms and stir over low heat (do not let boil) for a couple of minutes until the sauce thickens. Remove from heat and serve immediately.