Preheat your oven to 180ºC/160ºC Fan/Gas 4. Line a 12 hole muffin tin with cupcake wrappers. I like to use cupcake wrappers from Purple Cupcakes. In a stand mixer, or large bowl using a hand mixer, cream together the Stork/butter and caster sugar until light and fluffy.
Crack the eggs into a jug and lightly whisk. Add the eggs to the butter and sugar mix, then the vanilla extract.
Add the flour and cocoa powder, mixing until only just combined - don't overmix. Fill the cupcake wrappers until approximately two thirds full using the ice cream scoop (or spoons, if you prefer).
Bake for around 18-20 minutes until ready. A skewer or toothpick inserted into the top of the cupcake will come out clean when they're ready. Remove from the oven and allow to cool on a wire rack.
When the cupcakes are cool, use an apple corer or similar to remove a section from the middle of each cupcake. Add a teaspoon of blackberry jam as a filling. You could also just use a knife for this.