1. Preheat the oven to 350F.

2. Combine the soup, milk, mushrooms, half the fried onions, the pimientos and black pepper in a large bowl and mix well.

3. Combine the green beans and half the soup mixture in a separate large bowl and mix well. Divide the mixture between two 1 1/2-quart baking dishes. Top with remaining soup mixture.

4. Bake for 20 minutes. Sprinkle the remaining fried onions on the tops. Bake until browned, about 5 minutes.

Tip: Smaller Batch
If you’re not serving a crowd, simply halve the amounts of the ingredients and bake the casserole in one baking dish.