Depending on how lean your bacon is, you may need to pour out some of the rendered fat before adding the shallots. Slideshow: Delicious Casseroles
Preheat the oven to 400°.
In a large nonstick skillet, brown the bacon over medium-high heat until crispy, about 4 minutes. Remove to a towel-lined plate. Add the shallots and sauté over medium-high heat until golden, about 4 minutes. Add the spinach and cook until wilted, about 2 minutes.
In a small bowl, whisk together the milk and cornstarch. Add to the pan and Simmer until slightly thickened, about 3 minutes. Season with the nutmeg, salt and pepper to taste.
Transfer the spinach to a 1-quart ceramic baking dish. Sprinkle the breadcrumbs over the top, followed by the bacon. Bake for 10 minutes, until heated through.