Chocolate Chip Hamantaschen

Name: Chocolate Chip Hamantaschen
Ingredients: 1 cup confectioners’ sugar; 2 large egg yolks; 8 ounces unsalted butter at room temperature, in small pieces; Grated zest of 1 lemon; 2 1/4 cups all-purpose unbleached flour; Dash of salt; 1 large egg, beaten, for the glaze; 3 egg yolks; 1/4 cup sugar; 1 1/4 tablespoons cornstarch; 2 teaspoons unsweetened cocoa powder; 3/4 cup milk; 1/2 vanilla bean, split lengthwise; 2 ounces bittersweet chocolate, roughly chopped; 2 1/2 ounces semisweet chocolate chips