Preheat the oven to 350F/177C convection (325F/163C conventional) and grease and line an 8x8” pan with baking spray and parchment paper (leaving an overhang to easily remove them).
Place the chocolate in a medium, heat proof bowl and set it aside.
1 cup (6oz) semi-sweet chocolate chips
If the butter is cold, cut it into cubes and place it into a light colored, medium size saucepan, over medium-low heat. Use a wooden spoon or rubber spatula to stir the butter occasionally. It will begin to bubble, continue stirring intermittently.
1 cup (227g) salted butter
Once it begins to foam, you won't be able to see what's happening so stir continuously, making sure to scrape the solids off the bottom of the pan. The milk solids will begin to settle on the bottom of the pan and darken in color.
Remove from the heat and continue stirring for another minute or so, until the butter darkens into an amber color. Pour the butter, with all the little solid bits over the chocolate and allow it to rest for a minute.
Then stir the chocolate and butter together until the chocolate is completely melted and smooth.
In a separate large bowl, place the granulated sugar, brown sugar, cocoa powder, vanilla and eggs. Whisk them together aggressively for 2-3 minutes, until the mixture is completely smooth.
1 cup (200g) granulated sugar, 1/2 cup (95g) light brown sugar, 3 large eggs, 1 tsp vanilla extract, 3/4 cup (60g) Dutch-process cocoa powder
Add in the melted chocolate and butter and whisk until the mixture is fully combined.
Add in the flour and salt and whisk just until there’s only a few streaks of flour left.
1/2 cup (60g) all-purpose flour, 1/2 tsp fine sea salt
Fold in most of the M&Ms, reserving just a few for topping, until they're evenly dispersed.
2/3 (135g) mini M&Ms
Spread into the prepared pan and top with the reserved handful of M&Ms. Bake for 40 minutes. The top should be thin and crackly and puffed in the enter.
Tap it against the counter a couple of times, it should deflate a little but not be jiggly at all. When you press on it, it should feel soft underneath but not liquid-y.
Allow to cool in the pan for 30-60 minutes. Top with a pinch of sea salt flakes and serve warm or cooled.
pinch sea salt flakes