Sourdough Discard Halloween Kitchen Sink Cookie Bars

5 from 1 vote

A fun "kitchen sink" style cookie bar that is perfect for Halloween! Packed with chocolate chips, M&Ms, pretzels, Halloween sprinkles, and more!

Prep Time15

Cook Time40

Total Time55

Course: Dessert

Cuisine: American

Servings:

Calories: 240kcal

Preheat the oven to 350℉ (175℃) and line a 9x13-inch baking pan with parchment paper (this is optional, but makes it easier to remove the cookie bars after baking). Set aside.
In a medium bowl, whisk together flour, salt, baking soda, cornstarch, and baking powder. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or in a large mixing bowl with a hand-held mixer), cream the butter and sugars until light and fluffy, 2-3 minutes.
Add the egg, vanilla extract, and sourdough discard and mix on low until smooth and combined.
Add the flour mixture and mix on low until combined. Stir in the chocolate chips, M&Ms, pretzels, and sprinkles until combined.
Using a large cookie scoop or spoon, roughly scoop the cookie dough into the prepared 9x13-inch baking pan. Use your hands or a spatula to evenly press the cookie dough to the edges of the pan and fill any spaces.
This doesn't need to be too precise - the dough will rise and spread as it bakes, filling in any small gaps or rough spots!
Optional: Sprinkle extra M&Ms and crushed pretzels on top of the dough. If using Halloween googly eyes, lightly press those into the top of the dough.
Bake for 35-40 minutes until browned and the cookie bars are set on the edges. Let cool in the baking pan for at least 30 minutes before transferring to a cooling rack to cool fully. Slice into bars, then serve!
Pro tip: Before serving, add a few more googly eyes! They tend to melt during baking, so add more after baking!