Make the Frangipane: Whisk together 3 tablespoons of melted unsalted butter with ¼ cup of granulated sugar and one egg yolk until smooth. Add 1 teaspoon of vanilla extract and ½ teaspoon of almond extract, mixing well. Gradually fold in ½ cup of ground almonds, 2 tablespoons of all-purpose flour, and a pinch of salt. Set aside.

Prepare the Dry Ingredients: In a separate bowl, combine 1 cup of all-purpose flour, ½ teaspoon of baking powder, ¼ teaspoon of baking soda, and a pinch of salt. Whisk together until evenly combined.

Cream the Wet Ingredients: Beat ½ cup of room temperature unsalted butter with ½ cup of brown sugar and ¼ cup of granulated sugar until light and fluffy. Add 2 egg yolks, 1 teaspoon of vanilla extract, and ½ teaspoon of almond extract, beating until pale.

Combine Mixtures: Gradually add the flour mixture and ½ cup of ground almonds to the creamed mixture, mixing on low speed until just combined.

Shape the Cookies: Form small balls of dough, place on baking sheets, create an indent in each, and fill with frangipane. Top with sliced almonds.

Bake: Preheat oven to 350°F (175°C). Bake cookies for 12-13.5 minutes or until edges are lightly golden. Centers should remain soft.

Cool & Serve: Let cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely. Dust with powdered sugar before serving.