Step 1In the bowl of a stand mixer, or in a large bowl using an electric mixer, mix together the flour and powdered sugar. With the mixer running, start adding the butter cubes and continue mixing until all the butter is added and the mixture has a wet sand-like consistency.
Step 2Make an indentation in the middle of mixture and add the egg yolk and water. Mix just until all of the ingredients are combined to form a dough. Form the dough into a flat square and wrap tightly in plastic wrap. Chill until the dough is firm, at least 30 minutes.
Step 3Remove the dough to a lightly-floured work surface and roll to a thickness of about 1/8-inch. Use a 3-inch round cutter to cut 20 circles from the dough. Arrange the circles on 2 parchment-lined baking sheets and refrigerate for at least an hour.
Step 1In the bowl of a food processor, pulse the almonds until they are very-finely ground. With the processor running, add the agave and almond extract in a slow stream until the mixture comes together to form a ball. Add the sugar and pulse until it is incorporated, then the egg white. Continue running until the mixture again forms a ball, stopping and scraping the sides and bottom of the bowl once or twice if needed.
Step 2Refrigerate the paste for at least 30 minutes to cool, then divide the mixture into 20 balls (each using a heaping tablespoon of paste).
Step 1Heat the oven to 400 degrees. Place a ball of almond paste in the center of each dough circle. Fold the cookie dough around the ball and press in three places using your fingers. Bake the cookies until the tops of the balls and edges of the cookies are golden brown.
Step 2Place the cookies on a rack until they are cool, then dip the bottoms of the cookies in the melted chocolate. Invert the cookies so the chocolate can dry.