Heat your over to 180°C/160°C fan/355°F/Gas mark 4.
Grease your 2lb loaf tin and line with greaseproof (parchment) paper, ensuring that the paper overhangs the tin edges on the long sides so that you can hold it to remove the cake from the tin once baked.
Beat your softened butter a little, to ensure it is at the right texture, it should not clump around the beater paddle and it should be sticking to the outside of the bowl when ready, then add your sugar.
Beat until light and fluffy and paste-like, this can take several minutes to achieve. When ready the mixture should be soft and spreadable and stick to the outside of the bowl and not the beater. Scrape down with your spatula halfway through to ensure fully mixed in.
Sift together your flour, baking powder and salt into a separate bowl and set aside.
Add an egg to your butter and sugar mixture and beat in on a low setting. After a few beats wipe the bowl down with your spatula to ensure everything is equally mixed, then continue until mixed in.
Repeat the above step with your remaining eggs, with the last one add a spoonful of your flour mixture to prevent it from curdling.
Mix together your sour cream, milk and vanilla extract and then beat into the cake batter on a low setting.
Add your remaining flour mixture and beat in, starting on low, until incorporated. Again scrape down with your spatula halfway through to ensure all of the mixture is incorporated.
Give the cake batter a good beat on a medium-high setting for 10 seconds.
Fold your flour-coated white chocolate drops into the cake batter.
Add to your loaf tin and level out.
Pop over your halved flour-coated raspberries so that they sit on top of the cake batter.
Bake in the centre of your oven for 45-55 minutes, or until a metal skewer inserted into the centre of the cake comes out clean.
Allow to cool in the tin for 5 minutes, then lift out, holding the greaseproof paper, and place on a cooling rack to fully cool.