Pre-heat the oven to 338℉/170℃ and line a 20cm x 30cm deep baking tray with greaseproof paper.
Place the 250 g Guittard 70% Bittersweet Dark Chocolate Baking Bar and butter into a heat-proof bowl and melt slowly over a pan of simmering water until completely melted.
Meanwhile, place the eggs, muscovado sugar and 1 Tsp Prova Gourmet Madagascar Bourbon Vanilla Extract into a bowl of a stand mixer for about 5 minutes, or until doubled in volume or pale and fluffy.
Once the chocolate and butter mixture has melted and cooled slightly, whisk into the eggs and sugar mixture until fully incorporated.
Sift in the flour and baking powder then gently combine, being careful not to overwork the mixture.
Add in the rum-soaked raisins and mix.
Pour into the pre-pared baking tray and spread equally into the tray.
Sprinkle with the demerara sugar and 2 Tbsp Guittard Cocoa Nibs for an extra crunch when baked.
Bake for 25-30 minutes. Once baked, leave to cool before slicing, or place in the fridge to cut the day after to make it extra fudgy.
Enjoy!