Preheat the oven to 350F/180 C. Prepare a 8x8 inch square baking pan with parchment paper.
In a small pot, heat the butter and chocolate chips over medium heat until melted.
¾ cup unsalted butter, 1 cup semi-sweet chocolate chips
Pour the hot melted butter into a large bowl and whisk in the sugar.
1 ¼ cup white granulated sugar
Whisk in the eggs and egg yolk one at a time until combined and the batter starts to pull away from the sides of the bowl.
3 large eggs, 1 large egg yolk
Fold in the flour, baking powder, salt, and cocoa powder with a rubber spatula until just combined.
¾ cup all-purpose flour, ½ teaspoon baking powder, ½ teaspoon salt, ⅓ cup unsweetened cocoa powder
Pour the batter into the prepared baking pan and then sprinkle the almonds over the top.
⅓ cup almonds
Bake for 30 minutes, then take the pan out of the oven and sprinkle the marshmallows over the top. Return the pan to the oven for another 1-2 minutes until the marshmallows are puffy and lightly golden brown.
1 cup mini marshmallows
Remove the pan from the oven and let it cool completely on a wire rack.
Drizzle with melted chocolate and sprinkle with more chopped almonds and mini marshmallows if desired.
semi-sweet chocolate chips
When ready to cut, spray or butter a sharp knife to keep the marshmallows from sticking to it. Wipe the knife with a hot wet towel in between cuts to keep it from pulling the marshmallows off!