These Sourdough Discard Halloween Kitchen Sink Cookie Bars are an easy, festive way to use up Halloween candy. Packed with M&M’s, pretzels, Halloween sprinkles, and chocolate chips, they deliver a satisfying sweet-and-salty bite. The recipe is forgiving—swap in Reese’s Pieces or chopped chocolate candy if that’s what you have on hand.
Why you’ll love this recipe
- Simple one-pan baking. Make a full tray of cookie bars in one bake—no need for multiple cookie batches.
- Uses sourdough discard. This recipe calls for unfed discard, but you can substitute active starter if you prefer.
- Flexible mix-ins. Use any candy or chips you have: M&Ms, Reese’s Pieces, chopped chocolate bars, or festive sprinkles—great for using leftover Halloween treats.
- Freezer-friendly. These bars freeze well, so you can store extras for later.
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Ingredients
Below are the main ingredients needed to make these kitchen sink cookie bars. Quantities and full details are in the recipe card at the end.
- Sourdough discard: Unfed and at room temperature. This recipe is written for a 1:1 starter ratio; adjust if your starter differs.
- M&Ms (or other chocolate candies): Any size or variety works—use what you have.
- Chocolate chips or chunks: Dark, semisweet, or milk chocolate are all fine.
- Pretzels: Use any type; they’ll break up when mixed in so exact shape doesn’t matter.
See the full recipe card below for exact amounts and step-by-step directions.
Substitutions & Variations
This recipe is very adaptable. A few easy ideas:
- Active starter instead of discard: Swap 200 g active starter for the discard without changing other ingredients.
- Different chocolate: Use chocolate chunks, white chocolate, or whatever you prefer.
- Swap candies: Try Reese’s Pieces or chopped candy bars. Use seasonal sprinkles for other holidays.
How to Make Sourdough Discard Halloween Kitchen Sink Cookie Bars
These cookie bars come together in a few straightforward steps. The full, printable recipe is at the bottom of the post.
- Step 1: Whisk together dry ingredients and set aside.
- Step 2: Cream butter and sugars until light and fluffy.
- Step 3: Add the dry ingredients to the creamed butter mixture and mix until combined.
- Step 4: Fold in mix-ins—pretzels, M&Ms, chocolate chips, and sprinkles—until evenly distributed.
- Step 5: Press the dough evenly into a 9×13-inch pan (a cookie scoop helps). Top with extra pretzels, M&Ms, or sprinkles for decoration.
- Step 6: Bake for 35–40 minutes until the edges are set and golden. Cool in the pan for at least 30 minutes, then slice and serve.
Expert Baking Tips
- Pretzel texture: Pretzels will break up while mixing, so shape doesn’t matter and pre-crushing isn’t necessary.
- Sticky dough is normal: The dough will be a bit tacky—press it into the pan as evenly as you can; it will spread and smooth while baking.
- Top for presentation: Adding extra candy, pretzels, or sprinkles on top is optional but makes the bars look festive.
- Googly-eye sprinkles: These add a Halloween touch. If they melt in the oven, press a few more on after baking.
Storage
Room temperature: Store bars in an airtight container at room temperature for up to two weeks. They may firm up with time but remain tasty.
Freezer: Fully cooled bars can be frozen in an airtight container for up to three months. Thaw to room temperature before serving.
Recipe FAQs
Parchment is optional. It makes removing the bars easier, but can make spreading the dough slightly harder—choose whichever you prefer.
Cool in the pan for 30–60 minutes to make removal and slicing easier and neater.
More Sourdough Discard Cookie Recipes
- Sourdough Chocolate Chip Cookie Bars
- Sourdough Discard Shortbread Cookies
- Sourdough Discard Sugar Cookies
- Sourdough Lofthouse Cookies
If you try these Sourdough Discard Halloween Kitchen Sink Cookie Bars, please leave a star rating and a comment to share how they turned out. Happy baking!
Sourdough Discard Halloween Kitchen Sink Cookie Bars
Jessica Vogl
Pin Recipe
Equipment
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Kitchen scale
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9×13-inch baking pan
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Parchment paper optional
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3-Tablespoon cookie scoop
Ingredients
- 2 ¼ cups + 2 Tablespoons all-purpose flour
- 1 teaspoon kosher salt
- 1 teaspoon baking soda
- 1 ½ teaspoons cornstarch
- ½ teaspoon baking powder
- ½ cup unsalted butter softened
- 1 ¼ cup brown sugar packed
- ½ cup granulated sugar
- 1 egg
- 2 teaspoons vanilla extract
- 200 grams (about ¾ cup) sourdough discard unfed, at room temperature
- 6 ounces chocolate chips
- 6 ounces M&Ms plus more for topping
- 1 cup pretzels plus more for topping
- 2 Tablespoons Halloween sprinkles
Instructions
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Preheat oven to 350℉ (175℃). Line a 9×13-inch pan with parchment if desired and set aside.
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Whisk together flour, salt, baking soda, cornstarch, and baking powder in a medium bowl; set aside.
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In a stand mixer with the paddle attachment (or with a hand mixer), cream butter and sugars until light and fluffy, about 2–3 minutes.
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Add the egg, vanilla, and sourdough discard and mix on low until smooth and combined.
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Mix in the flour mixture on low until combined, then stir in chocolate chips, M&Ms, pretzels, and sprinkles.
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Scoop the dough into the prepared pan using a large scoop or spoon. Press the dough evenly to the edges with your hands or a spatula. The dough will spread as it bakes.
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Optional: Press extra M&Ms, pretzels, or googly-eye sprinkles onto the top. If using edible eyes, you may want to add a few after baking so they don’t melt.
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Bake 35–40 minutes until the edges are set and golden. Cool in the pan for at least 30 minutes, then transfer to a cooling rack, slice, and serve.