2 packages (10 ounces each) frozen chopped spinach, thawed and squeezed dry
1 pound large fresh mushrooms
2 tablespoons finely chopped onion
4 tablespoons butter (divided)
4 bacon strips, cooked and crumbled
1 cup milk
1 cup (8 ounces) shredded cheddar cheese
1/2 teaspoon ground mustard
1/2 teaspoon salt
1/2 teaspoon salt

Place spinach in a greased 8-in. baking dish and set aside. Remove stems from mushrooms and set caps aside. Chop stems. Sauté chopped stems and onion in 2 tablespoons butter until soft and then spoon over the spinach. Sprinkle with bacon then top with mushroom caps. Melt the remaining 2 tablespoons of butter and brush over the caps.

In a large saucepan, combine the milk, cheese, mustard, salt and pepper. Cook over medium-low heat, stirring constantly, until cheese is melted and then pour over the top.

Bake, uncovered, at 350° for 35-40 minutes or until mushrooms are tender.