1. Preheat the oven to 375°F. Lightly grease a 2-quart au gratin or other shallow baking dish. Arrange the chicken slices in the dish.

2. Half-fill a large saucepan -with cold water and bring to a boil over high heat. Add the broccoli, return to a boil, and cook, uncovered, for 2 minutes or until crisp-tender. Drain, rinse with cold water, and dram again. Arrange in a single layer on top of the chicken.

3. In a medium-size saucepan, bring the milk and stock to a simmer over moderate heat. In a small bowl, whisk together the sour cream, cornstarch, Parmesan cheese, sherry, mustard, salt, nutmeg, and ground red pepper. Whisk into the broth mixture and simmer, uncovered, for 5 minutes or until slightly thickened, stirring frequently. Pour the sauce over the chicken and broccoli. Sprinkle the Cheddar cheese and bread crumbs over the top.

4. Bake, uncovered, for 20 to 25 minutes or until hot and bubbly. Preheat the broiler and broil 4 inches from the heat for 2 minutes or until golden. Serve with freshly baked Portland Popovers.