Sirloin Stroganoff Bake

Ingredients

• 1 Beef Top Sirloin Steak Boneless (about 1 pound), cut into thin strips
• 12 ounces uncooked short pasta (like rigatoni, cavatappi, or fusilli)
• Kosher salt and black pepper, to taste
• 2 tablespoons olive oil
• 2 tablespoons butter
• 1 small yellow onion, thinly sliced
• 12 ounces mushrooms, thinly sliced
• 3 cloves garlic, minced
• 1 tablespoon Dijon mustard
• 1 tablespoon Worcestershire sauce
• 1 teaspoon fresh thyme or 1/2 teaspoon dried
• 1-1/2 cups shredded mozzarella cheese
• Additional sour cream and chives (optional)
• Sour Cream Bechamel:
• 3 tablespoons butter
• 3 tablespoons all-purpose flour
• 2 cups whole milk
• 3/4 cup sour cream
• 1/2 cup grated Parmigiano Reggiano cheese
• 1 pinch nutmeg