Prepare 2 circular baking tins (I use 20cm tins) with non-stick baking paper in the bottom. Preheat your oven to 160C Fan / 180C.
Place your butter and sugar into a bowl and cream together until light and fluffy (I use an electric hand whisk).
Add your eggs, one at a time mixing between each addition. Also add your vanilla at this point.
Fold in your flour and baking powder carefully. Followed by optionally your lemon zest.
Carefully fold in your prosecco followed by your chopped strawberries. Make sure your prosecco is properly folded in. The mixture is looser than a regular victoria sponge batter.
Spoon / pour your cake mix into the tins equally and place in the oven for about 25 minutes.
Whilst your cakes are in the oven make your syrup. Place your Prosecco and caster sugar into a saucepan and heat until the sugar dissolves. Bring it to the boil and allow to simmer for about 3-5 minutes until the mix is slightly more syrupy. Put to one side.
Remove your cakes from the oven, they should be lovely and golden. Allow to cool briefly in their tin (5 minutes) before turning out onto a cooling wrack. Whilst the cakes are still warm, spread a little of the Prosecco syrup on each. You don't need to use too much per sponge, a couple of tbsp would be fine, the more you use the more delicate the sponges will be, but they do taste good! Allow to cool completely.
To make your buttercream, place your butter in a stand mixer (or electric hand whisk if you don't have a stand mixer), mix on its own on a high speed for about 5 minutes. The butter should change from a more yellow colour to being a lot more pale.
Add your icing sugar gradually to the butter (I do this in two stages). I mix each addition of icing sugar for around 3-5 minutes before adding the second half.
Add the prosecco syrup gradually a tbsp at a time and mix. I wouldn't use more than about 4 tbsp as the buttercream might get runny. Buttercream should never be runny!! (If you've made your butter cream dairy free I would use less prosecco syrup and place it in the fridge to firm up first).
Finely slice your strawberries for each layer. If they have been soaking in prosecco, remove and lightly dry them before slicing. Keep a few nice ones for the top.
Place your bottom cake layer on your cake stand. Add a good amount of the buttercream and spread it. Place a layer of sliced strawberries on top - make sure you have plenty right round the edges so you can see them! Place your second cake layer on top. Spread more icing on top of the cake, then finish with fresh strawberries.
Slice and enjoy!