Slice the trifle sponges in half, then sandwich with raspberry jam.
Arrange in a large bowl, pour over the sherry and sprinkle with flaked almonds. Keep a few almonds back to decorate the top later.
To make the fresh custard: Pour 600ml milk into a non-stick saucepan. Warm up over a medium heat.
In a bowl break the eggs and beat well, add the vanilla essence, sugar and remaining 150ml milk; mix well. Add to the saucepan of milk, stirring with a wooden spoon.
Continue to heat but don't let it boil or you will end up with scrambled eggs! Keep heating and stirring all the time until the custard coats the back of the spoon and has become thicker. Remember, patience is a virtue. The trick is to get it thick without boiling and thereby going lumpy.
Have a washing-up basin full of cold water ready and when the custard is the right consistency, hold the saucepan in cold water for a few minutes, stirring all the time to reduce the temperature quickly.
Pour half the custard over the sponge cakes, cutting the sponges a little to allow the custard to soak in. Then pour over the remaining custard.
Leave to cool in the fridge. After several hours, when cold, whip the cream and spread over the top of the trifle.
Scoop 6 or 8 cherries out of the jar and place onto kitchen paper to absorb some of the liquid. Place on top of the trifle.