These brownies are super chocolaty but they do have a relatively tender crumb so I don’t recommend adding nuts. As for the oil, if you don’t have coconut oil at home, I imagine that olive oil would work just fine and if you’re looking to make these completely vegan, substitute flax eggs for the whole eggs called for here, and you’ll be good to go.
Heat the oven to 350°F and prepare the pan: Line an 8×8 square baking pan with parchment paper, and grease the parchment paper and pan with a little coconut oil.
In a small mixing bowl, whisk together the cornstarch, almond meal, cocoa powder, baking powder, and salt.
Take 2 ounces of the dark chocolate and coarsely chop it. Set it aside. Take the other 6 ounces and add it to a small saucepan along with the coconut oil. Over low heat, warm them, stirring until the chocolate is completely melted, about 2 minutes.
Pour the chocolate mixture into a large bowl. Whisk both sugars and vanilla extract into the chocolate mixture, stirring vigorously until combined. Fold in the eggs.
Add the dry ingredients and stir until well combined. Fold in the 2 ounces chopped chocolate. The batter will be quite thick —it won’t be loose and thin like many traditional brownie batters.
Scoop the batter into the prepared pan, and use a rubber spatula to smooth it into the pan in an even layer.
Bake the brownies for 30 minutes, or until the edges are set and no longer jiggly. The tops of the brownies will still feel soft; they’ll firm up as they cool.
Let the brownies cool completely before slicing, at least 2 hours.
Slice, serve, and store: Using the parchment paper as a handle, lift the cooled brownies up out of the pan and onto a cutting board. Slice. Leftover brownies can be stored in an airtight container at room temperature for up to 3 days.