Preheat the oven to 180 degrees/gas mark 4. Mix together the butter and sugar in a bowl until you have a soft, even texture. Next, gradually add the eggs and flour, folding as you go. Once you’re happy with your cake mixture, add 1 tsp of vanilla and mix.
Remove the cupcakes from the tin to cool on a wire rack, and prepare your buttercream. Mix together the butter and icing until you are happy with the consistency of your icing.
Using a small knife, cut a cylinder out the centre of the cupcake (I just draw a circle with the knife and remove the cake). In the hole, place a small dollop of jam (about half a teaspoon) and carefully replace the cake lid.
Use a piping bag, and decorate your cakes with a neat swirl, covering the cylindrical incision, and place half a jammy dodger on the top. Make sure you store the cakes in an airtight container to prevent the biscuits going soft.