Heat the oven to 180°C.
Grease the sides and bases of two cake tins and line the base with baking paper.
Cream the butter and sugar until light and fluffy.
Gradually add the eggs and keep beating. Fold in the lemon zest and elderflower, then sift in the flour.
Equally divide the batter between the two tins and put these in the oven.
Bake for about 25-30 minutes until springy and cooked through (insert a skewer inserted in the center, if it comes out clean - it's done).
Leave the cakes in the tins and using a tooth pick, prick all over the surface.
Meanwhile make the syrup: heat the sugar, elderflower and lemon juice gently in a pan until the sugar has dissolved and it has reduced to a syrupy liquid. Let it cool.
Drizzle the cakes with this syrup, and let them to cool completely before removing from the tins.
Whilst the cake is cooling make the filling: mix the mascarpone in a bowl with the lemon zest and elderflower.
In another large bowl, whisk the cream until you get firm peaks. Fold this in the mascarpone.
Add the icing sugar and taste. Add more sugar to your liking.
Take the cakes out of their tins carefully.
Place one cake on a serving plate and spread the top with the Mascarpone filling (you can add a layer of jam or lemon curd too).
Put the other cake on top and spread the mascarpone cream all over.
Decorate with berries, edible glitter, candies, crystallized petals etc suitable for the occasion.