1. Combine currants and almond liqueur in a small bowl. Let soak until fruit is plump, 30 minutes.

2. Preheat oven to 350 degrees. In a medium bowl, whisk together cornmeal, flour, sugar, baking powder, and salt. In a separate bowl, whisk together egg and egg yolk, lemon zest, and vanilla. Using a pastry cutter or two knives, cut butter into dry ingredients until coarse crumbs form. Add plumped currants and wet ingredients, gently stirring until a soft dough forms. Turn dough out onto a piece of plastic wrap. Shape into a flat square, wrap tightly in plastic, and refrigerate 45 minutes or up to overnight.

3. On a lightly floured surface, roll out dough to an 8-inch square, about 1/2 inch thick. Using a sharp knife, cut dough horizontally into 1-inch strips. Working with one strip at a time, cut crosswise on the bias into 5 equal diamonds (you should make 6 cuts). Reroll scraps once and form additional cookies, if desired. Transfer cookies to two parchment-lined baking sheets, spaced about 1 inch apart. Freeze until firm, about 10 minutes.

4. Lightly beat reserved egg white. Brush tops of cookies with egg white and sprinkle with sanding sugar. Bake, rotating pans halfway through, until lightly golden around edges, about 22 minutes. Cookies can be stored in an airtight container at room temperature up to 3 days.