Mushroom Stroganoff

• 
  
  8 ounces medium pasta shells
• 3 tablespoons unsalted butter
• 1 1/2 pounds cremini mushrooms, thinly sliced
• 2 large shallots, diced
• Kosher salt and freshly ground black pepper, to taste
• 3 cloves garlic, minced
• 4 teaspoons chopped fresh thyme
• 2 1/2 tablespoons all-purpose flour
• 2 cups beef stock
• 1 1/2 teaspoons Dijon mustard
• 3/4 cup sour cream
• 2/3 cup freshly grated Parmesan
• 2 tablespoons chopped fresh parsley leaves

1. In a large pot of boiling salted water, cook pasta according to package instructions; drain well.
2. Melt butter in a large skillet over medium high heat. Add mushrooms and shallots, and cook, stirring occasionally, until mushrooms are tender and browned, about 5-7 minutes; season with salt and pepper, to taste.
3. Stir in garlic and thyme until fragrant, about 1 minute.
4. Whisk in flour until lightly browned, about 1 minute
5. Gradually whisk in beef stock and Dijon. Bring to a boil; reduce heat and simmer, stirring occasionally, until reduced and slightly thickened, about 4-5 minutes.
6. Stir in pasta and sour cream until heated through, about 1-2 minutes. Stir in Parmesan until melted, about 1 minute. Stir in parsley; season with salt and pepper, to taste.
7. Serve immediately.