If you want to infuse your strawberries with prosecco, place fresh strawberries in a bowl, pour prosecco over the top so they are mainly submerged and allow them to sit in it for at least a couple of hours. This is optional, but I love the taste!
Prepare 3 circular baking tins with parchment paper in the bottom. Preheat your oven to 160C Fan.
Put all your cake ingredients into a large mixing bowl and mix. I just used an electric hand whisk for this. Mix until combined and smooth. (Make sure your butter is softened before you start or else it will just be lumpy!)
Spoon / pour your cake mix into the tins and place in the oven for about 25 minutes. (I always ensure the cake tins are on the middle shelf so if you have to do two tins first and then the third tin afterwards, that's fine).
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 (5-10 minutes) before turning out onto a cooling wrack. Whilst the cakes are still warm, spread a little of the Prosecco syrup on each - I used my silicone pastry brush. You can gently prick the cakes and then drizzle the syrup on but I find just carefully brushing them with the syrup is enough. You only need to use a tbsp per layer I find. Leave them to completely cool.
Make your buttercream. In a mixer or with your electric hand whisk cream until your butter is light and creamy. Then gradually add your icing sugar, mixing in between until it's fully combined. Add 2 tbsp on the prosecco syrup and mix again until combined. (If you've made your butter cream dairy free I would place it in the fridge to firm up, otherwise it's read to use).
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 whole 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! Repeat this until all 3 tiers are on. On the top of the cake spread a little more icing, more centrally only this time. Then place your whole strawberries on top.
Slice and enjoy!
Making this a two tiered cake: