Preheat the oven to gas mark 4/350oF/180oC/160oC fan and line an 8 x 8 inch/20 x 20cm baking tin with parchment paper ensuring you leave some overhang to make removing the cake easier.
Add the raspberries to a blender and blend until fully broken down. Pour the raspberries into a saucepan and place on a medium to high heat. Heat while stirring for around 12 - 15 minutes to reduce the raspberries and get most of the water out.
When the raspberries have finished reducing you will be left with a thick purée. Pour the reduced raspberries through a sieve, pressing down on the raspberries with a spoon to help push it through the sieve. This is to remove the seeds. Set the reduced raspberries aside.
To a mixing bowl, add and cream together the sugar and butter until fluffy. Add in the oil and mix well. Mix in the eggs, vanilla extract and soured cream then add the reduced raspberries and pink food colouring if using. Add the salt and self-raising flour then combine until smooth.
Pour the batter into the lined baking tin and bake for 45 minutes. Test the cake is fully baked by inserting a skewer into the centre. If the skewer comes out clean then the cake is baked. Place the tin onto a cooling rack for 20 minutes then remove the cake using the parchment paper overhang and place it on a cooling rack still on the parchment paper.
Once the cake has cooled, make the glaze by combining the icing sugar and milk. Once smooth with no lumps, spread the glaze onto the cake and decorate with sprinkles.