Tuna Tetrazzini

Ingredients:

• 8 ounces thin spaghetti, cooked al dente and drained
• 6 tablespoons butter, divided
• 16 ounces thinly sliced mushrooms
• 1 large onion, sliced
• 4 Tablespoons all-purpose flour
• 2 cups milk
• 1/2 teaspoon salt, or to taste
• freshly ground black pepper to taste
• 2 cans (4 to 6 ounces each) tuna, drained and flaked
• 1 cup frozen green peas, cooked and drained
• 1 cup shredded natural Parmesan cheese, or about 1/2 cup finely grated Parmesan cheese
• 1 cup bread crumbs

Directions:
Heat oven to 350°F. Grease a 2 1/2- to 3-quart baking dish. In a large saucepan over medium-low heat, melt 4 Tablespoons of the butter. Add the mushrooms and saute, stirring, until mushrooms are browned and tender. Add the chopped onion and continue cooking for 1 minute. Stir in the flour until well blended. Gradually stir in the milk. Continue cooking, stirring constantly, until thickened. Add salt, to taste, and pepper. Stir in the flaked tuna and peas. Stir in the spaghetti until well blended. Turn the mixture into the prepared casserole. Sprinkle Parmesan over the casserole. Melt the remaining 2 Tablespoons of butter and toss with the bread crumbs. Sprinkle the buttered crumbs over the Parmesan layer. Bake for 25 to 30 minutes, until lightly browned and bubbly. Serves 6.