Preheat your oven to 400°F. Grease a casserole dish with a bit of neutral oil.
Place the chicken breasts in the casserole dish. Season them with salt, pepper, and paprika.
Cut the ham to match the size of the chicken breasts. Place on top and sprinkle with shredded cheese.
In a bowl, combine the heavy cream, milk, and mustard. Mix the cornstarch with a tablespoon of milk until smooth. Add it to the cream mixture. Stir everything well until the sauce slightly thickens. Season with salt and pepper.
Pour the sauce evenly over the meat. In a saucepan, melt the butter, then stir in the breadcrumbs. Spread the breadcrumb mixture evenly over the casserole.
Bake for 30 minutes, or until the chicken is cooked through, the cheese melted, and the breadcrumbs golden brown. If the breadcrumbs brown too quickly, simply cover the casserole with aluminum foil and continue baking.
Remove the casserole from the oven. Garnish with chopped fresh parsley, if desired, before serving.
