Heat the oven to 350°F and line a baking sheet with parchment paper.
In a mixing bowl, beat the softened butter and sugar until smooth and creamy.
Add the egg yolk and vanilla extract, then mix until fully combined.
Stir in the flour, baking powder, and salt until a soft dough forms.
Roll the dough into a ball, place it between two sheets of parchment, and roll to 1/4-inch thickness.
Cut the dough into 8 small circles or pumpkin shapes and transfer them to the baking sheet.
Bake for 8 to 10 minutes until the edges are lightly golden, then let the cookies cool completely on a wire rack.
Spread a thin layer of green buttercream frosting over each cooled cookie to create the patch base.
Pipe small orange pumpkins on top of the green frosting using the orange buttercream, adding a tiny stem with the green frosting if desired.