Put the brioche slices in a large shallow dish, whisk together the eggs and milk and pour over. Leave to soak for at least half an hour (this can be done the night before and kept in the fridge).
Heat the butter in a large frying pan and cook the brioche, a slice or two at a time, for 2 minutes on each side, or until golden brown and cooked through. Keep warm in a low oven and repeat until all the slices of brioche are cooked.
Cut the slices in half and arrange on a platter scattered with raspberries. Serve with raspberry jam for spreading.