In the bowl of a stand mixer fitted with the paddle attachment, beat butter, granulated sugar, and corn syrup at medium speed until fluffy and light in color, 2 to 3 minutes, stopping to scrape sides of bowl. Add eggs and vanilla, beating until combined; scrape sides and bottom of bowl. Add melted chocolate, and beat until lighter in color and well combined, stopping to scrape sides and bottom of bowl.
½ cup unsalted butter, 1 ¼ cup granulated sugar, 2 tablespoons light corn syrup, 2 large eggs, 2 teaspoons vanilla extract, 2 ounces unsweetened chocolate
In a medium bowl, whisk together flour, cocoa, baking soda, baking powder, and salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating just until combined after each addition and stopping to scrape sides of bowl. Loosely cover with plastic wrap, and refrigerate for 1 hour.
1 ¾ cup all-purpose flour, ½ cup unsweetened cocoa powder, 1 teaspoon baking soda, ½ teaspoon baking powder, ½ teaspoon kosher salt
Preheat oven to 350°F (180°C). Line 2 baking sheets with parchment paper.
In a small bowl, place sanding sugar or sprinkles.
Using a small spring-loaded cookie scoop, scoop dough, and roll into 1-inch balls. Roll in sanding sugar or sprinkles. Place 2 inches apart on prepared pans.
red and green sanding sugar or sprinkles
Bake until tops are slightly cracked, 8 to 10 minutes. Let cool on pans for 2 to 3 minutes. Using your thumb or the back of a teaspoon, gently make an indentation in center of cookies. Remove from pans, and let cool completely on wire racks.