Lamb tetrazzini

Pasta, cooked	8 ounces
Lamb leg or shoulder, cooked, cut into 1-inch cubes	1 pound
Oil, olive	2 teaspoons + 2 teaspoons
Mushrooms, sliced	½ pound
Onion, finely chopped	1 small
Milk	2 ¾ cups
Flour, all-purpose	¼ cup
Salt	½ teaspoon
Pepper, freshly ground	¼ teaspoon
Cheese, Parmesan, grated	¼ cup
Butter	2 tablespoons
Bread crumbs	1 cup

1. Preheat the oven to 350°F; grease an 11-by-7-inch casserole dish. 
2. In a large skillet, heat 2-teaspoons oil over medium-high heat. 
3. Add the lamb, and cook for 6 minutes, stirring to brown on all sides; transfer to a bowl with the cooked pasta. 
4. In the same skillet, heat 2-teaspoons oil, and then add the onion and mushrooms; cook for 3 minutes. 
5. Whisk the milk and flour together until smooth, then add the milk mixture to the skillet with salt and pepper. 
6. Cook over medium heat, stirring, until slightly thickened, then stir in the cheese. 
7. Pour over the pasta and lamb, tossing to coat well; pour into the casserole dish. 
8. In a small skillet, melt the butter. 
9. Remove from heat, and stir in ¾-cup breadcrumbs. 
10. Sprinkle over the casserole with the remaining crumbs. 
11. Bake for 25 to 30 minutes, until bubbling and slightly browned on top.