Heat oven to 400° F. Lightly coat a medium baking dish with vegetable cooking spray. Mince the garlic in a food processor, then add the parsley and pulse until combined, about 15 seconds. Add the bread, Parmesan, oil, salt, and a few grinds of black pepper. Pulse until well combined. Arrange the meat or fish in the baking dish. Spread with the mustard, then pat the crumbs on top.
Bake until cooked through, 20 to 25 minutes for the chicken, 30 minutes for the pork, or 20 minutes for the salmon. Divide among 4 plates and season with salt and pepper to taste.