Spread your favorite jam on 12 slices of the bread (fruit jams or jelly are best rather than marmalade).
Cover with another slice of the crustless bread and cut the sandwich into any shape you want, into thre pieces to make a Bismark type of doughnut, or cut them into four squares, whatever pleases you.
Beat the eggs, milk, sugar and Vanilla together.
LIGHTLY DIP both sides of the dougnut in the egg mixture (do not soak the doughnut).
When deepfryer has reached the right temperature (375-380f) drop in a few doughnuts and fry about 2 minutes on each side. It is extremely important that you have the temperature high enough and do not soak the bread in the egg just dip them or you will end up with soggy, greasy lumps.
They should be golden and crisp.
Wait a few minutes between batches to ensure the temp is hot enough or you will end up with a grease soaked doughnut.
Drain on a rack.
If you wish you can drizzle icing sugar over them just after you remove them from the fryer or have them plain.