Preheat the oven to 350 °F (177 °C) Add parchment paper or silicone baking mats to two cookie sheets.
Beat the eggs, sugar, light brown sugar, butter, corn syrup, and vanilla until fluffy. In a different bowl, whisk the cocoa powder, flour, salt, cornstarch, and baking soda together. Slowly beat the dry ingredients into the wet ones to form the cookie dough.
Use a cookie scoop and scoop the dough into your hand and then roll it into a ball. Place on the cooking sheet and then press down to make a thick flat cookie.
Bake the cookies in the oven for 15-18 minutes. Let them cool completely.
Use the mixer to beat the powdered sugar, butter, whipping cream, and vanilla until a peak forms. Scoop it into a frosting bag and spiral it on top of the cookie. Sprinkle chopped-up heath bar candies on top.
Notes
Room temperature ingredients: Make sure your butter and eggs are at room temperature before starting. This helps them blend together smoothly and creates a better cookie texture. Cold butter won't cream properly with the sugars.
Use dark cocoa powder: Hershey's Special Dark cocoa powder is key to getting that rich, deep chocolate color and flavor that makes these cookies taste just like Crumbl. Regular cocoa powder will work but won't give you the same intense chocolate taste.
Don't skip pressing the dough: After rolling the dough into balls, make sure to press them down into thick disks before baking. This helps them bake evenly and gives you that perfect thick, chewy center with crispy edges.
Watch the baking time closely: These cookies are done when the edges are set but the centers still look slightly underdone. They'll continue to bake on the hot pan after you remove them from the oven, so don't overbake or they'll be dry instead of chewy.
Let cookies cool completely before frosting: This is super important! If you frost warm cookies, the frosting will melt and slide right off. Wait at least 30 minutes for the cookies to cool to room temperature before adding the vanilla frosting.
Use a piping bag for professional results: For that signature Crumbl swirl, use a piping bag fitted with a large star tip. If you don't have one, a zip-top bag with the corner snipped off works great too! Just make sure to cut a larger opening for those pretty swirls.
Crush Heath bars right before using: For the freshest flavor and best texture, chop your Heath bars just before topping the cookies. Pre-chopped toffee bits can work in a pinch, but freshly chopped Heath bars give you bigger, crunchier pieces.
Line your baking sheets: Always use parchment paper or silicone baking mats to prevent sticking and ensure even baking. This also makes cleanup so much easier!
Make them uniform: Using a cookie scoop (about 2-3 tablespoons) ensures all your cookies are the same size so they bake evenly. Nobody wants some cookies overdone while others are underbaked!
Beat the frosting long enough: When making the vanilla frosting, beat it for a full 3-5 minutes until it's light, fluffy, and holds stiff peaks. Under-beaten frosting won't pipe nicely and will be too runny.