Preheat the oven to 160C/gas 3. Line a 22cm square brownie tin with baking paper.
In a large bowl combine all the ingredients, except the peanut butter and raspberries, until smooth. Pour the batter into the lined cake tin. Add peanut butter into the mixture and use a skewer or knife to create a swirl pattern. Repeat the process with mashed raspberries.
Bake for 20-25 minutes, checking at 15 minutes to ensure the mixture is not burning. The brownies are cooked when the top is slightly firm to the touch. Try not to over cook. Allow the brownies to cool for 10 minutes before removing from the pan and slicing.