In a small saucepan, melt butter; stir in flour & cook until lightly browned. Slowly whisk in chicken broth. Add mustard & cook until thickened, stirring constantly. Set aside.
Pasta & Filling
Cook pasta shells in boiling, salted water with a few drops of oil added for 10-12 minutes. Drain, rinse in cold water, drain again. Grate Gouda cheese. In a saucepan, fry bacon to a soft crisp stage, blot on paper towel & chop.
In a large bowl, combine ground turkey, onion, garlic, Parmesan, soy sauce, basil, thyme, 1/2 of chopped bacon, salt & pepper. Add a small amount of prepared sauce (to help to hold filling together).
Preheat oven to 350 F. Using a 9-inch baking dish, spread some sauce over the bottom. Divide turkey filling between shells. Place filled shells, single file in pan. Pour remaining sauce over all & top with remaining bacon. Sprinkle smoked Gouda cheese evenly over top. Cover & bake for 30-40 minutes or until filling is cooked.