In a medium bowl, whisk together flour, baking powder, and salt. In a large bowl, beat 1 cup butter and granulated sugar until light and fluffy. Add the egg and 1 teaspoon vanilla extract, mixing until combined. Gradually add the dry ingredients to the wet ingredients, mixing until a dough forms. Divide the dough into three parts and wrap each in plastic wrap. Chill for at least 1 hour.

Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper. On a floured surface, roll out the dough to about 1/4-inch thickness. Use round cookie cutters of different sizes to cut the dough. Place on prepared baking sheets and bake for 8-10 minutes until edges are lightly golden. Cool on a wire rack.

Beat 1 cup of butter until creamy. Gradually add powdered sugar, 1 cup at a time, beating until smooth. Add 2-3 tablespoons heavy cream, 1 teaspoon vanilla extract, and green food coloring. Mix until you achieve desired consistency and color.

Use frosting to stack different sizes of cookies to form a tree shape. Pipe frosting between each layer and on top to add dimension. Decorate with edible pearls and star-shaped sugar decorations.