Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper.
In a mixing bowl, combine the flour, baking powder, garlic powder, salt, and black pepper. Mix well.
In another bowl, beat the softened butter until creamy. Gradually add the flour mixture, mixing until combined. Stir in the Parmesan cheese and parsley if using.
Spread a generous layer of the butter mixture onto one side of each slice of bread.
Place the slices butter-side up on the prepared baking sheet.
Bake in the preheated oven for 10-12 minutes, or until the edges are golden brown and crispy.
Remove from the oven and let cool slightly before serving.