01 -
Let the whole pan hang out on a rack until it's not warm at all, then cut it up.
02 -
Pop it in the oven for 45 to 50 minutes. The sides shouldn't be wobbly and a toothpick stuck about 2 inches in should only show some crumbs. Want them extra fudgy? Take 'em out before they're too dry.
03 -
Spread the mix in your pan and scatter the M&M's all over so you get some in every bite.
04 -
Toss in the cocoa powder and salt. Pour in the vanilla too. Stir just until it comes together, then go easy folding in the flour—some streaks are just fine.
05 -
Add one egg, give it a whisk, and keep going one by one until the mix looks paler and glossy.
06 -
Using a bowl over a pot with a couple inches of simmering water, melt butter and chocolate with both sugars, swirling the mix until it's shiny (even if it's a bit gritty). Take it off the heat and let it cool a bit.
07 -
Crank up your oven to 350°F. Put parchment paper inside an 8x8 pan, letting it hang over the sides. Give the bottom a quick spray so nothing gets stuck.