Preheat your oven to 180°C (356°F) and line a small 15cm baking tray with parchment paper.

Melt 100g of butter in a medium saucepan over low heat. Stir in 150ml of milk, 200g of granulated sugar, and 1 tsp of vanilla extract until smooth, about 2-3 minutes.

Add 150g of chopped dark chocolate to the saucepan and stir continuously until melted and smooth.

In a separate bowl, sift together 100g of all-purpose flour, 30g of cocoa powder, and a pinch of salt. Fold the dry mixture into the wet mixture until just combined.

Pour the batter into the prepared baking tray and spread it evenly.

Bake in the preheated oven for about 20 minutes until the top is crackly and the edges pull away.

Allow the brownies to cool in the tray for at least 30 minutes.

While cooling, melt the remaining 150g of dark chocolate in a saucepan and stir in 3 tablespoons of peanut butter until smooth.

Once cooled, pour the ganache over the brownies, spreading it evenly, and refrigerate for at least 1 hour.

Lift the brownies out using the parchment paper edges, slice into squares or rectangles, and serve.