Pre-heat your oven to 140C Fan/160C/325F/Gas Mark 3, and line a cupcake tin with cupcake cases
For the cupcake sponge, mix together the baking spread and caster sugar, ideally using an electric hand mixer or in a stand mixer with the paddle attachment, for 5 minutes until smooth and fluffy
Add the eggs and prosecco extract (if using), and mix them in well
Then gently whisk, or fold in, the self raising flour
Divide the mixture between the cupcake cases, and bake them for 25-30 minutes or until a thin skewer inserted in the centre of the cupcakes comes out clean. Put them on a rack to cool completely
While the cupcakes are baking, make the syrup. Put the caster sugar and prosecco in a pan on a low heat, stir together until the sugar is dissolved
Bring to the boil and let boil for 3 minutes, then take off the heat and leave to cool completely
Use a cupcake corer or a knife to make a hole in the centre of each cake, drizzle each cupcake with about 1 tsp of the prosecco syrup, then fill the holes with the strawberry jam
To make the buttercream, mix the softened butter on it's own for a few minutes. Then add the icing sugar and prosecco syrup, and mix until smooth. You can do this by hand, but an electric hand whisk or stand mixer with paddle attachment will provide the best results. If the buttercream is too stiff, you can add a little more prosecco syrup
Put into a piping bag fitted with your chosen nozzle and pipe it on top of each cupcake
Add the fresh strawberries and sprinkles on top to decorate
Store leftovers in an airtight container in a cool place and eat within 3 days