Line an 8" square tin. Melt the Peanut Butter for about 30 seconds – 1 minute in the microwave, until loosened. Spread this over the lined 8 inch square tin in an even layer and freeze for 15 minutes before starting the brownies! You can use this tin for the brownies later.
Preheat the oven to 200C/180C Fan/Gas 6. Line an 8" Square Pan.
Start by melting the dark chocolate: break up the dark chocolate and melt in the microwave in 20 second intervals, stirring in between to make sure it doesn’t burn. Set aside to cool a little whilst doing the rest:
Combine the melted butter, granulated sugar and light brown sugar in a large bowl/bowl of a stand mixer – on a medium speed for 3-5 minutes.
Add in the eggs and vanilla and mix again. Then, checking first that the chocolate isn't so hot as to cook the eggs, add it in and keep mixing.
Add the flour, cocoa powder, chopped chocolate and peanut butter chocolates and fold in gently.
Remove the tin with the peanut butter from the freezer. Peel off the layer of peanut butter from the greaseproof paper and set aside. Place the greaseproof paper back into the tin for the brownies. Pour half the brownie batter into the tin, add the whole square layer of solid peanut butter on top, then cover with the remaining batter. Bake 30 minutes.
Let cool before decorating (if doing so). Simply microwave the peanut butter in a small bowl to loosen, then drizzle over. Add any chopped chocolate/peanut butter chocolates. Slice with a hot knife and serve!