Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and grease and line two 8" cake tins (that are at least 2" deep)
Make the sponge by mixing the butter and caster sugar in a large bowl, ideally with an electric mixer, until fluffy and pale
Add the eggs and vanilla extract, and whisk until fully incorporated
Add the self raising flour and whisk in gently until you can't see any flour anymore
Divide the mixture between the tins, use scales for accuracy
Bake them for 35-40 minutes or until a skewer inserted in the middle comes out clean. Leave them to fully cool either in the tins or on cooling racks
While the cake is 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 2-3 minutes, then take off the heat and leave to cool completely
If the cakes have domed on top, level them off with a cake leveller or a serrated knife
Poke the cakes all over with a thin skewer, then brush the syrup evenly over them
To make the buttercream, mix together the butter and icing sugar, this is best done using an electric mixer
When it starts to come together add the prosecco, and whisk until smooth
Put one of the sponges on your plate or cake stand, and pipe a border of buttercream around the edge of the sponge. Fill the centre with the strawberry jam
And the second sponge on top, pipe larger rosettes of buttercream all around the edge and smaller ones in the centre
Decorate with the fresh strawberries and sprinkles, if using
Serve immediately, store leftovers in an airtight container in a cool place and eat within 3 days