01 -
Start by preheating your oven to 350°F (177°C). Lightly coat a 9×13 inch casserole dish with nonstick cooking spray to prevent sticking.
02 -
In a large bowl, combine the yellow cake mix, eggs, vegetable oil, and vanilla extract until well blended. The mixture will be thick and sticky. Gently fold in the colorful Easter M&M candies and semi-sweet chocolate chips until they're evenly distributed throughout the batter.
03 -
Spread the cookie bar dough evenly into your prepared dish, smoothing the top with a spatula. Pop it into the preheated oven and bake for 20-25 minutes, or until the edges are lightly golden and the center is just set. Don't overbake if you want them chewy!
04 -
Allow the cookie bars to cool completely in the pan before cutting. This helps them set up properly. Once cooled, slice into squares and serve.