Layers of sponge alternate with layers of sweetened cream and lemon butter, while the cake's sides are coated with toasted flaked almonds for an elegant presentation. Vigorous whisking of the eggs and sugar ensures that this sponge rises perfectly.
Sponge Cake: Preheat the oven to 190 degrees C. Grease and ﬂour two sandwich tins, 22 cm in diameter and line the bottoms with nonstick baking paper.
Whisk the eggs and caster sugar in a large mixing bowl or a food mixer until they are very thick, pale and creamy and will hold a ribbon trail of the mixture almost indefinitely.
Sift the ﬂour over the egg foam mixture and fold it in carefully with a whisk or large metal spoon, then gently fold in the butter. Divide the batter equally between the two tins and tap gently to level the mixture.
Bake the cakes in the preheated oven for 20–25 minutes, or until well risen, firm and springy to the touch and slightly shrunk away from the sides of the tins.
Allow to cool in the tins for 1–2 minutes, then loosen the sides with a knife and transfer to a wire rack to cool completely. When the cakes are cool, make the filling.
Filling: Whisk the cream with the sugar and vanilla until thick but not buttery.
To Assemble: Using a very sharp knife, carefully cut each sponge cake in half horizontally.
Put 2 tablespoons of the lemon butter in a small paper piping bag and refrigerate. Place one sponge layer on a ﬂat serving dish and spread with a third of the remaining lemon butter followed by a layer of cream. Place another sponge layer on top and spread with more lemon butter and cream. Repeat with the third layer, then place the final layer on top and press together gently.
Spread cream around the side of the cake and coat with the ﬂaked almonds, brushing away the excess nuts when the side is well covered.
Put 2 tablespoons of the remaining cream into a piping bag fitted with a small star nozzle, then spread the rest evenly over the top of the cake, marking it decoratively with a palette knife. Pipe eight small rings of cream around the top of the cake (one on each slice), then fill each ring with the reserved lemon butter. Chill until required.