Preheat the oven to 350°F (180°C or gas mark 4) and place a piece of parchment paper on a half sheet pan (13 x 18 inch [33 x 45 cm]).

Place the frozen raspberries in a microwave-safe bowl and microwave in 30-second intervals until they are thawed and have released their juices. Mash until smooth.

In a large bowl, combine the flour, baking powder, cacao powder and brown sugar. In a separate bowl, combine the melted dark chocolate and butter, room-temperature milk, vanilla and ⅓ cup (85 g) of the peanut butter.

Pour the wet mixture into the dry and stir well, then transfer the batter to the parchment-lined sheet pan. Push the mixture into the corners.

Carefully mash the thawed raspberries with a potato masher or fork. Spoon the raspberries on top of the brownie mixture in lines, from one of the longest sides of the pan to the other.

Repeat with the remaining half of the peanut butter so it’s spread just underneath each mashed raspberry line.

Use a knife or skewer to make lines from one short side to the other and then repeat in the opposite direction to create the swirls. Top with the halved fresh raspberries and peanut halves and place the pan in the oven to bake for 15 to 20 minutes, or until firm but still a bit gooey inside.

Allow the brownies to cool for 10 minutes before cutting into portions. Enjoy.