Heat the oven to 350 degrees and line a baking sheet with parchment paper.

Whisk the flour, matcha powder, baking powder, and salt in a bowl until evenly combined.

Cream the butter and granulated sugar in a separate bowl until light and fluffy.

Mix in the egg yolk and vanilla extract until smooth.

Add the dry ingredients to the wet mixture and stir until a dough forms.

Roll the dough to 1/4 inch thickness on a lightly floured surface and cut into rounds.

Place the rounds on the prepared baking sheet and bake for 10 to 12 minutes until the edges are set.

Cool the cookies completely on a wire rack.

Stir the powdered sugar with enough milk to reach a thick piping consistency.

Add black food coloring until the icing reaches a deep black shade.

Pipe simple cat silhouettes onto each cooled cookie and let the icing set before serving.