Preheat an oven to 320 degrees  and line a 9" or 10" cake tin with baking paper.

In a saucepan, place the butter, sugar, milk and white chocolate. Leave on a low heat and stir occasionally to ensure it doesn't catch and burn. Continue until the chocolate and butter is melted and the sugar dissolved.

Once melted, leave to cool for 20 minutes or until cooled.

While waiting to cool, sift the flours and baking powder into a large bowl, add the pistachios and make a well in the center to add the wet mixture.

Once the white chocolate mixture has cooled, add the eggs and vanilla paste to it and mix well.

Add the white chocolate mixture to the flour gradually (I suggest 2-3 sections) and mix in between each addition. If using an electric mixer, use the lowest speed and you should just be folding the two together.

Once the flour mixture and white chocolate mixtures are combined, add the raspberries and very gently fold through the mixture.

Place mixture into the tin and bake for approximately 1hr - 1 and a half hours- this will all depend on the size/shape of your tin (I use both round and square) Ensure that you keep an eye on the cake towards the end of baking time. I find baking times sometimes change depending on raspberries used.

As all ovens are different, I suggest you keep an eye on the cake and turn the tin if needed. Test the cake to see if is ready by sticking a knife or skewer into the cake- if it comes out clean, it is ready. The top of the cake will become golden, if you think it is becoming too golden for your liking, turn the oven down 10 degrees and cover the top with baking paper, but cooking time may increase.

Leave the cake to cool in the tin for at least 20-30 minutes and then turn onto a cooling rack. Dust with icing sugar (confectioners sugar) once cool and before serving. If desired, a buttercream icing also goes very well with this cake.

Due to it's density, this cake stores well in an airtight container and can be made a day ahead.