Step 1In the bowl of a stand mixer, or in a large bowl using an electric mixer, cream together the butter and sugar. Beat in the egg yolk until incorporated, then beat in the almond extract.
Step 2Beat in the salt, then slowly beat in the cake flour until fully combined. Beat in one-half cup ground almonds. Wrap the dough in plastic wrap and chill thoroughly.
Step 3Heat the oven to 375 degrees. On a floured surface, roll one-fourth of the dough at a time (keep the remainder covered and chilled) to form a log approximately one-half inch thick. Cut the log crosswise every inch for each cookie. Repeat until all of the dough is rolled and cut.
Step 4In a small bowl, beat the egg white. In a shallow baking dish, whisk together the remaining one-half cup ground almonds with the coarse sugar.
Step 5Brush the surface of each cookie lightly with egg white, then dip the surface into the coarse sugar and almond mixture.
Step 6Place the cookies about 1 inch apart on an ungreased baking sheet and bake until set and golden on the bottom, about 10 to 12 minutes. Cool the cookies on a rack. Store the cookies in an airtight container. The cookies can be made up to 2 months ahead and frozen; thaw before serving.