Preheat the Oven: Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
Mix Dry Ingredients: In a medium bowl, whisk together almond flour, all-purpose flour, baking powder, and salt. Set aside.
Cream Butter and Sugars: In a large bowl, use a hand mixer or stand mixer to cream together the softened butter, granulated sugar, and brown sugar until light and fluffy (about 3-4 minutes).
Add Wet Ingredients: Beat in the egg, vanilla extract, and almond extract (if using) until well combined.
Combine Mixtures: Gradually add the dry mixture to the wet mixture, mixing until just combined. Do not overmix.
Shape Cookies: Using a tablespoon or cookie scoop, portion out the dough and roll it into balls. Place them on the prepared baking sheets, leaving space between each cookie. Flatten each ball slightly with the palm of your hand.
Add Almonds: Press a few sliced almonds onto the top of each cookie for decoration.
Bake: Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden. The centers may look slightly underbaked, but they will firm up as they cool.
Cool: Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.
Serve: Enjoy your almond cookies with a cup of tea or coffee!