Put the buttermilk in a shallow bowl. In another shallow bowl, mix breadcrumbs, parsley, mustard powder, salt and pepper. Dip the trouts in buttermilk, letting drain the excess , then put in the breadcrumbs flipping them to coat well (shake to remove the excess).
Put the trout fillets on a baking sheet that has oiled foil on it. Sprinkle almonds on them and drizzle with butter. Cook in a preheated oven of 450 F 8 to 12 minutes per inch of thickness or until it flakes easily with a fork.