Place the milk and vanilla extract onto the saucepan, over a medium heat and bring to the boil.
In the meantime, in. a bowl, beat the egg yolks and sugar for 1 minute until thick then stir in the corn flour.
Now pour the warm milk over the egg yolks mixture.
Return the entire mixture to the saucepan and slowly cook over a gentle heat, stirring continuously until the egg custard start to thicken and coats the back of the spoon.
Remove immediately from the heat, and leave for 20 minutes to cool.
Next, prepare the berry compote.
Place the berries in a heavy-based pan with the sugar and Grand Marnier, then bring to the boil, stirring so that the sugar dissolves. Continue to boil fast for about 5 minutes until the berries are tender but still holding their shape.
When the custard and berries are cool. Start to build the trifle.
Place the swiss roll pieces in a bowl, drizzle with sherry and pour the custard over the sponge mixture and allow to cool for a couple of hours or overnight. Cover with a disc of parchment paper or cling film to prevent the formation of a crust.
When ready to serve, pipe some whipped cream on the top and sprinkle, if desired, with some toasted flaked almonds and fresh berries.