Dorie Greenspan's Double-Buckwheat Double-Chocolate Cookies - Chew Nibble Nosh

Ingredients

• 1 2⁄3 cups (227 grams) all-purpose flour
• 1 cup (120 grams) buckwheat flour
• 1⁄4 cup (21 grams) unsweetened cocoa powder
• 2 sticks (8 ounces; 226 grams) unsalted butter, cut into chunks, at room temperature
• 1⁄2 cup (100 grams) sugar
• 1⁄4 cup (50 grams) packed light brown sugar
• 1 teaspoon fine sea salt
• 2 large egg yolks, at room temperature
• 1 teaspoon pure vanilla extract
• 1⁄4 cup (45 grams) kasha, preferably Wolff’s medium granulation (see headnote)
• 4 ounces (113 grams) bittersweet chocolate, finely chopped
• 2 teaspoons sanding sugar, mixed with 1 teaspoon flake sea salt, such as Maldon, for sprinkling