In a large mixing bowl, combine 2 cups of all-purpose flour, 1 teaspoon baking powder, and 1/2 teaspoon salt. Add 2 tablespoons of melted butter and pour in 3/4 cup of milk. Mix until a soft dough forms, ensuring there are no dry spots. Knead the dough lightly on a floured surface for about 2 minutes until smooth, then cover and let it rest for 15-20 minutes.

After resting, divide the dough into 15 equal portions. Roll each piece into a ball, then flatten into a 5-inch circle using a rolling pin. Prick each circle with a fork multiple times. Heat a deep skillet with about 2 inches of oil over medium heat.

Carefully place one dough circle in the hot oil. Fry for approximately 1 minute or until it begins to float and puff up. Using tongs, gently fold the chalupa in half while frying, maintaining the shell shape. Fry for an additional minute until golden brown and crispy.

Remove from the oil and drain on paper towels. Repeat for the remaining dough circles, ensuring the oil temperature is maintained.

Prepare your toppings while the chalupa shells cool slightly. Drain black beans and warm them over medium heat. Chop lettuce and tomatoes into bite-sized pieces. Set out bowls of sour cream, queso sauce, and shredded cheese.

Fill each chalupa shell with a layer of warm black beans, followed by lettuce, diced tomatoes, sour cream, and queso sauce. Optionally sprinkle cheese on top. Serve your homemade chalupas immediately.