Prepare the Cookies : Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper. In a large mixing bowl, cream together the softened butter, granulated sugar, and powdered sugar until light and fluffy. Beat in the eggs, one at a time, followed by the vanilla and coconut extracts. In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Fold in the shredded coconut until evenly distributed. Scoop tablespoon-sized portions of dough onto the prepared baking sheets, spacing them about 2 inches apart. Flatten slightly with your fingers or the back of a spoon. Bake for 10-12 minutes or until the edges are lightly golden. Let the cookies cool completely on a wire rack.

Make the Lemon Curd Filling : In a small saucepan, whisk together the lemon juice, lemon zest, granulated sugar, and egg yolks over medium heat. Add the butter cubes and cook, whisking constantly, until the mixture thickens enough to coat the back of a spoon (about 5-7 minutes). Remove from heat and strain the lemon curd through a fine-mesh sieve to remove any lumps. Let it cool completely.

Assemble the Cookies : Spoon a dollop of cooled lemon curd onto the flat side of one cookie, then top with another cookie to create a sandwich. Dust the tops with powdered sugar and sprinkle toasted shredded coconut for an extra touch of flavor and texture.