6 tablespoons butter, plus more for baking dishes
Coarse salt and ground pepper
1 pound penne rigate
1 teaspoon olive oil
2 boneless, skinless chicken breast halves (8 ounces each), halved horizontally
1/2 cup plus 2 tablespoons all-purpose flour (spooned and leveled)
4 garlic cloves, minced
6 cups whole milk
10 ounces white mushrooms, trimmed and thinly sliced
1/2 cup oil-packed sun-dried tomatoes, drained and thinly sliced
1 1/2 cups shredded provolone (6 ounces)
1 cup finely grated Parmesan (4 ounces)