Remove and grease your slow cooker pot.
In a bowl, mix the flour, caster sugar, baking powder, lemon zest and a pinch of salt.
250 g self-raising flour, 140 g caster sugar (superfine sugar), 1 tsp baking powder
Add the butter and mix.
100 g butter
Whisk together the eggs, milk, lemon juice in a jug, then pour this onto the dry ingredients and mix till smooth.
3 medium free-range eggs, 150 ml milk, zest and juice of two lemons
Stir in the berries, then pour the mixture into the slow cooker pot.
250 g blueberries, 125 g raspberries, 150 g sweet blackberries
In a jug, mix together 250 ml boiling water with the flesh from the lemons and leave to infuse for five minutes.
250 ml boiling water, The flesh from the two lemons used for zest and juice
Strain out the lemon, keeping the water, then mix in the 100 g of caster sugar and stir until dissolved.
100 g caster sugar (superfine sugar)
Pour this mixture over the batter in the pot.
Cover and cook on high for approx 2 hours, or until the sponge is firm and no liquid areas remain. It normally takes just over two and a half hours on high to cook in my slow cooker, which is quite slow.