- Portion size 6 servings
MethodIn large saucepan, melt butter over medium heat; cook onion, thyme and garlic, stirring occasionally, until slightly softened, about 4 minutes.
Stir in mushrooms; cook until softened, about 3 minutes. Add flour; cook, stirring, for 2 minutes. Gradually whisk in milk; cook, stirring, until thickened, about 5 minutes. Add mustard, salt and pepper. Stir in cheese until smooth.
Meanwhile, in large pot of boiling salted water, cook pasta until al dente, about 8 minutes. Drain and add to sauce; toss to coat. Discard thyme. Transfer to large ovenproof dish.
Topping: Combine bread crumbs with Parmesan cheese; sprinkle over macaroni mixture. Broil until browned, about 2 minutes.