Combine flour, salt, and baking powder in a large bowl, then cut in the cold butter until the mixture resembles coarse crumbs.

Gradually add milk and mix until a soft, pliable dough forms.

In a separate bowl, mix the cooked chicken, cream cheese, cheddar cheese, chopped green onions, garlic powder, and black pepper until well combined.

Roll out the dough on a lightly floured surface to about 1/4 inch thickness, then cut into 25 equal squares.

Place a spoonful of chicken filling in the center of each dough square, fold the corners to the center, and pinch to seal, forming a pillow shape.

Bake in a preheated oven at 375°F (190°C) for 20-25 minutes, or until golden brown and cooked through.