• Preheat oven to 350°F. Line two cookie sheets with a silicone baking mat. (or parchment paper)
• Using a standing mixer with paddles attached, cream 1½ cup unsalted butter, softened, 1½ cup light brown sugar, packed, ½ cup granulated sugar3 large eggs, room temperature, 2 Tablespoons light corn syrup, and 1 Tablespoon pure vanilla extract until light and fluffy, about 5-7 minutes.
• In a medium-sized mixing bowl, whisk 4 cups all-purpose flour, 1 cup dark cocoa powder, 1 Tablespoon cornstarch, 2 teaspoons baking soda, and 1 teaspoon kosher salt.
• Gradually beat the dry ingredients into the wet until a dough forms.
• Using a medium cookie scoop, scoop out dough mound into your hand and roll into a ball. Place onto the cookie sheet and light press into a thick disk.
• Bake in the preheated oven for 15-18 minutes or until firm around the edge.
• Allow to cool for a few minutes on the baking sheet. Then move the cookies to a cooling rack to cool completelly.

To make the vanilla frosting

• Use a standing mixer with paddle attachment, beat 1 cup unsalted butter, softened , 3 cups confectioners' sugar, 4 Tablespoons heavy whipping cream, 2 teaspoons pure vanilla extract until combined, smooth and stiff peaks form.
• Scoop the frosting into the piping bag. Pipe a tight spiral onto the top of the cookie.
• Sprinkle chopped Heath bars on top of each cookie.