Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and line a cupcake tin with cupcake cases
To make the sponge, mix together the butter, caster sugar, and lime zest, ideally using an electric mixer, until smooth
Add the eggs and vanilla extract and whisk well
Then gently whisk in the self raising flour
Divide the mixture between the 12 cupcake cases
Bake them for 20-25 minutes or until they are golden and a skewer inserted in the centre of the cupcakes comes out clean. Leave to cool completely
Use a cupcake corer or a knife to make a hole in the middle of each cupcake
Fill the holes with the passion fruit curd. You can do this using a spoon or put the curd into a small piping bag, snip the end off and pipe it in
Make the buttercream by mixing together the butter and icing sugar, then add the prosecco (or prosecco flavouring and milk), and mix until smooth. You can do this by hand or for best results use an electric whisk. If the buttercream is too stiff, you can add a little milk to loosen it
Pipe the buttercream onto each cupcake using a piping bag fitted with your chosen nozzle. Or spread on with a spoon
Cut the passion fruits in half and scoop out the seeds and pulp, drizzle it over the buttercream
Store in an airtight container in a cool place, eat leftovers within 3 days