Cream the light brown sugar with the butter until creamy.
Grease the slow cooker put then put the sugar and butter mixture in the bottom of the pot, spreading it around the base evenly.
Chop the strawberries and place the strawberries and raspberries over the bottom of the slow cooker on top of the butter/sugar mixture.
Put the cake ingredients in a bowl and mix together thoroughly.
Spoon the cake mixture on top of the strawberries.
Replace the lid, bake on high 1.5 to 2 hours or until a skewer comes out of the centre clean, with a tea towel under the lid to catch the condensation.
Remove the pot from the slow cooker, allow to cool slightly, then run a knife around the cake, invert the pot and carefully catch the cake on your hand, and then transfer to a plate to serve.