Preheat the oven to 350°F (180°C). Butter and line an 8x8 - inch square cake pan, which is what I used for a deep brownie. This is a big batter. You can also bake this in a 13x9-inch pan too, but the time will change to 40 minutes- judge it to keep the jiggle!

In a medium microwavable bowl, combine the sugar, water, and chocolate. In the microwave or over a bain-marie heat this mixture gently until the chocolate has melted, roughly 2-3 minutes. Allow this mix to cool slightly.

Into the cooled chocolate mixture whisk in the oil, eggs, and vanilla.

In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt. Add the dry ingredients into the wet ingredients and mix until just combined, do not over mix.

Into the batter swirl in 1/2 cup of peanut butter leaving big streaks throughout. Pour the batter into your prepared cake pan and finish by swirling in the remaining 1/4 cup of peanut butter on top and scattering over the chopped peanuts.

Bake for roughly 55-65 minutes. Always bake brownies a little under so that they remain fudgy on the inside. Once baked allow to cool in the pan for 30 minutes before cutting them. Enjoy warm with vanilla ice-cream.

Cover and store at room temperature for up to 4 days. They also freeze really well for up to 4 weeks.