Preheat oven to 350°F (175°C).

Saute the mushrooms in margarine until softened.

In a separate pot, heat the water and dissolve the bouillon cubes.

Set the bouillon mixture aside.

In another saucepan, melt 1/2 stick of margarine.

Sprinkle the flour over the melted margarine and stir to form a roux.

Gradually add the light cream to the butter/flour mixture, stirring constantly to prevent lumps.

Add the bouillon mix to the cream sauce.

Add the sauteed mushrooms to the cream sauce.

Butter a large casserole dish.

Pour the mushroom mixture into the buttered casserole dish, ensuring the mushrooms are in a single layer.

In a small bowl, combine the bread crumbs and Parmesan cheese.

Sprinkle the bread crumb and cheese mixture over the mushroom casserole.

Bake in the preheated oven for 30 minutes, or until golden brown and bubbly.

Let stand for 15 minutes before serving.