These squares should be damp and have a squidgy texture. This dampness means the squares keep well in an airtight container and should last a couple of days.
Prep time: 25 minutes
Cook time: 50 minutes
225g cold butter, chopped into chunks, plus extra for greasing
200g white chocolate, chopped
1 tsp vanilla extract
3 medium eggs
225g soft light brown sugar
150g plain flour, sifted
1. Preheat the oven to gas mark 4/180°C/fan oven 160°C. Grease an 18cm square cake tin and line the base with baking parchment.
2. Place the butter and half the chocolate in a heatproof bowl and set over a saucepan quarter-filled with simmering water (make sure the water doesn't touch the bowl). Heat, stirring, until the butter and chocolate are melted and smooth.
3. Remove from the heat and leave for 5-10 minutes to cool. Beat the eggs, vanilla extract and sugar together with an electric whisk for 5 minutes until they are thick and a pale toffee colour. Using a flexible, rubber spatula, fold the butter mixture into the egg mixture, a little at a time, trying not to knock out too much air.
4. Sift in the flour. Add the remaining chocolate chunks and the half the raspberries. Fold in to the mixture. Spoon into the prepared tin, scatter with the remaining raspberries and bake for 45-50 minutes or until risen and springy. Slice into 12 squares and keep in an airtight container. They will keep for 3-4 days.