Crepes with creamy chicken and mushroom filling

crepes

olive oil

Portobello mushrooms, sliced

cooked or grilled chicken, cubed

unsalted butter

all-purpose flour

and 1/2 cups milk

nutmeg

freshly ground Parmesan cheese

or 1/2 chicken bouillon cube, or more, to taste

salt

chopped green onions or chives, for garnish