01 -
Preheat the oven to 350°F (175°C). Line an 8-inch cast-iron skillet with parchment paper, or grease well if not using parchment.
02 -
In a small bowl, whisk together the flour, baking powder, and salt until well combined. Set aside.
03 -
In a large mixing bowl, use a hand mixer, stand mixer fitted with the paddle attachment, or a wooden spoon to mix together the melted butter, light brown sugar, and granulated sugar until smooth. Add the egg and vanilla extract, mixing until well blended.
04 -
Add the dry ingredients to the sugar mixture and stir until just combined. Do not overmix - stop when no dry streaks remain.
05 -
Gently fold in ¾ cup of the M&M candies, distributing them evenly throughout the dough.
06 -
Transfer the cookie dough to the prepared skillet and use your hands or the back of a spoon to press it evenly across the bottom of the pan.
07 -
Bake the cookie for 15 to 20 minutes or until the edges are lightly golden brown and the top of the cookie is set but still slightly soft in the center.
08 -
Place the skillet on a wire cooling rack and allow the cookie to cool for 10 minutes.
09 -
Place the milk chocolate chips in a microwave-safe bowl. Heat on high power for 30 seconds, then stir well. Continue heating in 15-second intervals, stirring after each, until the chocolate is completely melted and smooth.
10 -
Spread the melted chocolate evenly over the top of the warm cookie. Immediately press the remaining ¼ cup of M&M candies into the melted chocolate before it sets.
11 -
Allow the cookie pizza to rest for 15 to 20 more minutes, until completely cooled and the chocolate topping is set.
12 -
Cut into wedges like a pizza and serve. For clean slices, use a sharp knife and wipe the blade between cuts.