1. In a bowl, sift together the flour and cocoa powder. Add the salt and mix. In a small saucepan, place the butter and heat until melted. Add the chocolate and stir until it melts. Remove from the heat and set the chocolate-butter mixture aside. In a separate bowl or the bowl of a mixer, combine the eggs and both types of sugar. Whisk quickly with a whisk until the mixture is fluffy and the sugar has dissolved. Add the vanilla and mix. Add the chocolate-butter mixture and stir until the batter is homogenous. Add the flour mixture and fold in with a spatula using circular motions. Do not mix too fast, as we don't want to develop the gluten. Line a 20cm square baking pan with parchment paper. Pour the brownie batter into the pan. For the topping: Using a small spoon, dollop the crunchy peanut butter all over the surface of the brownie batter. Use the back of a spoon to swirl the peanut butter into the chocolate batter in circular motions. The peanut butter will be stiff to work with at first, but it will soften with the friction. Bake in a preheated oven at 170°C for 35 minutes. Let it cool completely before cutting, as the chocolate will still be runny right out of the oven.
