Prepare and bake the brownies according to the box directions for fudge texture in an 8x8-inch baking pan.
1 (18oz.) box brownie mix
While brownies are baking, add the flour and oatmeal to a small bowl and microwave for FIVE 15-second intervals, stirring between each one to heat treat the flour. The flour should reach a temperature of at least 160°F. Allow the flour to cool for 5 minutes after the last round.
1 cup all-purpose flour, ½ cup 1-Minute Oats
In a medium bowl, cream together the peanut butter, butter, light brown sugar, and granulated sugar until light and fluffy.
⅓ cup creamy peanut butter, ¼ cup unsalted butter, ¼ cup light brown sugar, ¼ cup granulated sugar
Beat in the heavy cream, vanilla, and salt until smooth. Then beat in the cooled flour until fully combined.
¾ cup heavy cream, 1 teaspoon vanilla extract, ¼ teaspoon salt
Use a rubber spatula to fold in the chocolate chips and M&Ms.
½ cup mini chocolate chips, ½ cup mini M&M's
Once the brownies have cooled, spread the cookie dough out on top of the brownies.
Then prepare the ganache by bringing the heavy cream to a low simmer in a small pot and pouring over the chopped chocolate in a heat-safe bowl. Let sit for 5 minutes.
4 ounces heavy cream, 4 ounces semi-sweet chocolate
Whisk the chocolate and heavy cream together until smooth, then whisk in the powdered sugar and vanilla extract.
¼ cup powdered sugar, 1 teaspoon vanilla extract
Pour and spread the ganache over the top of the cookie dough layer. Top with additional mini m&m's and sprinkles if desired and allow to set until cool before slicing.