Preheat oven to 400°. In a shallow bowl, mix bread crumbs and Parmesan cheese.
Sprinkle tops of cutlets with salt and pepper. Layer end of each with Gouda cheese and spinach. Fold cutlets in half, enclosing filling; secure with toothpicks. Brush mustard over outsides of pork; dip in bread crumb mixture, patting to help coating adhere.
Place on a greased foil-lined baking sheet. Bake until golden brown and pork is tender, 12-15 minutes. Discard toothpicks before serving.
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