Preheat oven to 350° F. Spray a metal 9x9 baking dish with non-stick spray and line with parchment paper.
Melt the butter and chocolate in a small bowl in the microwave, in 30 second intervals, stirring between each. When there are some lumps left, stir until they have melted and the mixture is smooth. Whisk in the cocoa powder. Set aside to cool a bit.
Add the eggs and granulated sugar to a large mixing bowl. Whisk for about 1-2 minutes, until the sugar is dissolved. You'll be able to feel this by rubbing a bit of mixture between your fingers - it should feel completely smooth. Whisk in the powdered sugar and vanilla. Then, pour the chocolate mixture into the bowl of eggs & sugar and whisk to combine. Stir in the almond flour and salt, folding in until just combined. Stir in ½ cup of chocolate chips, if desired.
Pour batter into your prepared pan and bake for 36 to 41 minutes. A toothpick inserted in the center should have thick batter (a mix of thick batter & moist crumbs is ideal). It shouldn't have all wet batter. A toothpick inserted in the edge will be almost clean. Don't over bake! The brownies will set up to the perfect fudgy consistency as they cool.
Let brownies cool in the pan for 1 hour before removing and slicing. Store cooled leftovers in an airtight container at room temp for 4-5 days.
