To make the lemon curd, whisk the eggs, sugar and yolks together in a bowl.
In a heavy-based pan, over a very low heat, gently heat the butter, zest and juice, until the butter has melted. Add the egg mixture and stir constantly over a low heat until it’s thickened. This will take 10 minutes or more. Don’t rush it or you’ll get scrambled eggs.
Strain the lemon curd mixture into a bowl and cover with a circle of baking parchment, or use clingfilm in contact with the surface, to prevent a skin forming, and allow to cool. If you are not using the curd immediately, strain into a sterilized jar, allow to cool and seal.
To assemble the trifle, line a 2 litre/3½ pint serving bowl with slices of Sicilian lemon and orange sweet bread, overlapping them slightly.
Drizzle the limoncello over the top and let it soak into the bread, then spread the lemon curd on top.
Break up the meringue nests and scatter them over the curd, followed by the custard generously spooned over the top.
Pour the cream into a bowl. Add the sugar and vanilla essence and whisk until it holds soft peaks when the whisk is removed. Spoon the cream over the top of the trifle in soft peaks. Scatter over the toasted almond and candied lemon zest. Chill until ready to serve.