Preheat the oven to 325 F. Line the bottom of a 9-inch springform pan with parchment paper, but do not grease the pan.
Whip the eggs and sugar on high speed until they are almost white in colour, more than triple in volume and hold a ribbon when the beaters are lifted, about 5 minutes. On medium speed, add the zest and juice.
Sift the flour and salt and, still on medium speed, add the flour. Spoon about a cup of the batter into a bowl, and stir in the melted butter and vanilla. Add this all back to the full batter and stir until blended. Pour the batter into the prepared pan and bake for about 40 minutes, until the centre of the cake springs back when gently pressed. Cool the cake completely in the pan.
For the cream, whip the cream until it holds a soft peak. In a separate bowl, beat the cream cheese to soften, and beat in the sugar, lemon juice and vanilla or vanilla bean paste. Fold in the whipped cream in 2 additions. Chill until ready to assemble.
When ready to assemble the trifles, put the cream in a piping bag fitted with a large plain tip. Stir the berries with the jam to coat. Slice the sponge cake in ½ horizontally then cut 12 circles of sponge cake using a cookie cutter about the same size as your individual trifle glasses (wine glasses or other pretty dishes). Spoon some of the strawberries into the bottom of the glass, then top with a disc of cake. Brush the cake with sherry. Top this with a piping of the cream and then repeat with the strawberries, sponge cake, sherry and cream. Use a vegetable peeler to create white chocolate shavings and sprinkle these on top of the trifles before chilling until ready to serve.
The trifles can be prepared up to 4 hours in advance.