Preheat the oven to 180 degrees Celsius.
In a pan on the hob, carefully melt the butter and the dark chocolate and mix together. Put to one side to cool.
Whisk together the eggs and the sugar until light and fluffy using an electric whisk or stand mixer. Pour the chocolate mixture into the whisked eggs and sugar and fold.
Add your flour, cocoa powder and peanuts. Fold again.
Pour half of the brownie mixture into a lined tin, then drizzle three quarters of the caramel on top. Pour in the rest of the mixture, drizzle with the leftover caramel and peanut butter, then swirl the brownie with a skewer to create a pattern. Decorate with small pieces of peanuts (optional).
Bake for 25-30 minutes, or until the middle no longer wobbles! Leave to set for a couple of hours, cut into squares and serve.