The center of these fluted sandwich cookies is filled in with apricot jam to give them the appearance of mini windows.
In a food processor, combine almonds and the 1 tablespoon sugar. Cover and process until nuts are finely ground. Set aside.
In a large bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add the 2/3 cup sugar. Beat until combined, scraping side of bowl occasionally. Add the finely ground almonds, the egg, egg yolk, salt, vanilla, almond extract, and nutmeg, beating on low speed until combined. Beat in flour until combined.
Divide dough into four portions. Cover and chill about 2 hours or until dough is easy to handle.
Preheat oven to 325 degrees F. Between waxed paper or parchment paper, roll out one of the dough portions to about a 1/4-inch thickness. Peel off top sheet of paper. Using a fluted 2-inch cookie cutter, cut out dough. Place dough cutouts 1 inch apart on an ungreased cookie sheet. Using a fluted 1-inch cookie cutter, cut out centers from half of the dough cutouts.
Bake in the preheated oven for 10 to 12 minutes or until tops are a pale golden brown. Cool on cookie sheet for 2 minutes. Transfer cookies to a wire rack; let cool. Repeat with the remaining dough portions.
Spread 1 slightly rounded teaspoon of the jam in the center of each whole cookie. Top with the cutout cookies, flat sides down, pressing lightly together. Makes about 30 sandwich cookies.
Layer assembled sandwich cookies between waxed paper in an airtight container; cover. Store in the refrigerator for up to 3 days or freeze for up to 1 month.