Instructions

• In the bowl of a stand mixer fitted with the paddle attachment (or in a large bowl with a hand mixer), combine ¾ cup softened unsalted butter, ¾ cup packed light brown sugar, ¼ cup granulated sugar, 1 large egg, and 2 teaspoons vanilla extract. Beat on medium-high speed until the mixture is well-creamed, light and fluffy—about 5 minutes with a stand mixer or about 7 minutes with a hand mixer.
• Stop the mixer and scrape down the sides and bottom of the bowl with a spatula.
• Add 2 cups all-purpose flour, 2 teaspoons cornstarch, 1 teaspoon baking soda, and a pinch of salt (optional and to taste). Mix on low speed (or stir by hand) until just combined, about 1 minute. Do not overmix.
• Add 1 heaping cup diced Snickers (diced small and loosely piled in the measuring cup) and 1 cup semi-sweet chocolate chips. Fold in by hand with a spatula or beat momentarily on low speed until evenly distributed.
• Use a medium 2-inch cookie scoop to portion the dough into heaping mounds (about 26 total). Place the mounds on a large plate or tray. Flatten each mound slightly with your palm, cover the tray tightly with plastic wrap, and refrigerate for at least 2 hours or up to 5 days. (Do not bake warm dough—cookies will spread too much if baked without chilling.)
• When you are ready to bake, preheat the oven to 350°F. Line a baking sheet with a Silpat, parchment paper, or spray it lightly with cooking spray.
• Place chilled dough mounds on the prepared baking sheet spaced at least 2 inches apart (about 8 cookies per sheet). If your dough was chilled overnight and you prefer, let the mounds sit at room temperature for about 15 minutes before baking. (Optional: rotate the baking sheet halfway through baking for more even browning.)
• Bake for 8 to 9 minutes, or until the cookie edges have set and the tops are just beginning to set (they may still look slightly pale and glossy in the center). Do not bake longer than 10 minutes; cookies will firm as they cool.
• Remove the baking sheet from the oven and let cookies cool on the baking sheet for 5 minutes. Then transfer the cookies to a wire rack to finish cooling.