Preheat oven to 320 degrees F (160 degrees C).
Fill a saucepan with a few inches of water, and bring to a simmer.
Place bowl on top of saucepan. Then add
Unsweetened Cocoa Powder (3/4 cup)
Unsalted Butter (2/3 cup)
Granulated Sugar (1 1/4 cups)
Salt (1/4 tsp)
. Allow the butter to melt completely.
Let rest until the butter has melted and stir.
Remove bowl from heat.
Vanilla Extract (1 tsp)
Large Eggs (2)
, one at a time. Stir well to combine.
All-Purpose Flour (2/3 cup)
Chocolate (1/2 cup)
if using. Stir thoroughly to combine, about one minute.
Pour mixture into floured baking tin.
Spread out mixture evenly in the pan.
Place in the oven and bake for 40 minutes, or until just set.