Dessert

Monster Mash Cookie Bars Recipe

ByLily Cross November 2, 2025November 2, 2025

Introduction

These Monster Mash Cookie Bars are a festive and fun treat perfect for Halloween or any spooky celebration. Loaded with chocolate chips, candy-coated chocolates, and candy eyeballs, they combine a chewy cookie base with festive decorations for a delightful twist.

The image shows a square piece of cookie bar with three visible layers on a white marbled surface: a dense, golden-brown bottom crust, a thick middle layer filled with colorful candy-coated chocolates mixed into a soft, light brown dough, and a slightly crumbly top with more scattered blue, orange, and purple candy pieces and two white candy eyes on top. The background has another cookie square slightly out of focus, and part of a woman's hand is visible holding one piece. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

1/2 cup unsalted butter, softened
1/2 cup brown sugar
1/4 cup granulated sugar
1 large egg
1 tsp vanilla extract
1 1/4 cups all-purpose flour
1/2 tsp baking soda
1/4 tsp salt
1/2 cup chocolate chips
1/2 cup Halloween M&Ms or candy-coated chocolates
1/4 cup candy eyeballs
Optional: sprinkles or chopped candy bars

Instructions

Step 1: Preheat your oven to 350°F (175°C) and line an 8×8-inch baking pan with parchment paper for easy removal.
Step 2: In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until the mixture is light and fluffy.
Step 3: Add the egg and vanilla extract to the creamed mixture, stirring until smooth and well combined.
Step 4: Stir in the all-purpose flour, baking soda, and salt until just combined, being careful not to overmix.
Step 5: Fold in the chocolate chips and Halloween M&Ms, reserving a few candies to press on top before baking.
Step 6: Spread the cookie dough evenly into the prepared pan, then press the reserved candies and candy eyeballs gently on the surface. Add sprinkles or chopped candy bars if desired.
Step 7: Bake for 20–25 minutes, or until the edges turn golden and the center is set but still soft.
Step 8: Allow the bars to cool completely in the pan before lifting out with the parchment paper and cutting into squares.

Tips & Variations

Use room temperature butter and eggs for easier mixing and a better texture.
Swap candy eyeballs for mini chocolate chips or colorful sprinkles to customize the look.
For extra chewiness, try adding a tablespoon of honey or molasses to the dough.
Use a mix of regular and peanut M&Ms if you want a nutty twist.

Storage

Store the cookie bars in an airtight container at room temperature for up to 4 days. They can also be refrigerated for up to a week; bring to room temperature before serving for the best texture. Reheat individual squares in the microwave for about 10 seconds if you prefer them warm.

How to Serve

A close-up image of a single square cookie bar on a white parchment paper, showing four thick layers: a firm golden-brown crust base, a gooey middle layer filled with melted chocolate chips and colorful candy pieces in orange, blue, purple, and green, topped with a crumbly golden crumb layer. The vibrant candy pieces and chocolate contrast against the tan cookie dough. In the background, more of the same cookie bars are slightly out of focus on a dark surface, with a white marbled texture beneath. photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I use a different size pan?

Yes, but adjust the baking time accordingly. A smaller pan will result in thicker bars and may need a few extra minutes, while a larger pan will produce thinner bars that bake faster.