Preparation

• Line a 9×5-inch loaf pan with waxed paper, letting the ends extend up the long sides by about 2 inches.
• In the bowl of a stand mixer fitted with the paddle attachment (or with a hand-held mixer and a large bowl), beat the butter and sugar until light, about 1 minute. Beat in the egg and vanilla.
• In another bowl, whisk the flour, baking powder, and salt; gradually beat the dry mixture into the butter mixture until blended.
• Divide the dough into three equal portions, and put each in a small bowl. Mix the almond extract and food coloring into one portion; spread evenly into the prepared pan. Mix the hazelnuts into another portion; spread evenly over first layer. Mix the melted chocolate and coffee extract into the remaining portion; spread on top. Cover with plastic wrap, and refrigerate overnight.
• Position a rack in the center of the oven, and heat the oven to 350°F. Loosen the unlined edges from the pan, then lift the waxed-paper edges to remove the dough. Cut the dough in half lengthwise, then cut each half crosswise into 1/8-inch-thick slices.
• Place the slices 1 inch apart on ungreased baking sheets. Bake until edges are firm (the cookies should not brown), 10 to 12 minutes. Transfer the cookies to wire racks to cool. Store in an airtight container for up to 5 days.