Please read About Soufflés.
Preheat the oven to 375°F. Generously butter an 8-cup soufflé dish or six 8-ounce ramekins and dust the insides with:
      1/4 to 1/2 cup dry breadcrumbs or grated Parmesan cheese
Shake out the excess. Heat in a small skillet over medium heat:
      1 tablespoon butter
Add and cook until softened, then set aside:
      2 tablespoons minced shallots
Prepare:
      1 1/2 cups Thick Sauce Béchamel, at room temperature or slightly warmed
Remove from the heat and add the sautéed shallots, along with:
      1 1/4 cups lightly packed grated Swiss cheese, Cheddar cheese or a combination of Swiss cheese and Parmesan cheese
      1/2 teaspoon salt
      1/8 teaspoon ground black pepper
      Pinch of ground red pepper
      Pinch of freshly grated nutmeg or ground nutmeg
      6 large egg yolks, added one by one
Beat vigorously to blend and set aside. Beat until stiff but not dry:
      6 large egg whites
      Pinch of salt
Stir one-quarter of the whites into the soufflé base to lighten it, then fold in the rest. Pour into the prepared soufflé dish or ramekins. Bake until the soufflé is risen and golden brown on top, 40 to 45 minutes (20 to 25 minutes for individual soufflés). Remove from the oven and serve immediately.