1 c. brown sugar, packed
1 Tbsp. vanilla extract
18 Oreo cookies, roughly chopped
1/2 c. M&M's
Preheat oven to 350 F.
Line an 8x8 inch baking dish with aluminum foil, then spray with cooking spray. Set aside.
In a large bowl, add the melted butter (slightly cooled), egg, brown sugar, and vanilla. Whisk until smooth.
Add in the flour, and stir until just combined.
Stir in the Oreos.
Stir in the M&M's and any sprinkles if you want them.
Turn the batter out into the prepared dish, smoothing it out lightly.
Place a few Oreos or M&M's or sprinkles (or all of them) on the top to be aesthetically pleasing.
Bake for 18-21 minutes, or until the top is set in the center. The bars will firm up as they cool. Place pan on a wire rack to cool for at least 90 minutes before slicing and serving. The filling in the Oreos has to re-solidify after melting, so this is why it takes 90 minutes before you can cut and serve.
Here's a link to the recipe I used: http://www.averiecooks.com/2015/11/loaded-mm-oreo-cookie-holiday-bars.html