Clean and wash spring onions and cut into fine rings. Peel, wash and roughly grate the potatoes. Mix potatoes, spring onions and egg. Season with salt and pepper.
Heat oil in a pan and fry 4 medium sized buffers until golden brown. Remove and degrease on kitchen paper. Stir crème fraîche until smooth and put 1 tablespoon on each buffer and cover with a lettuce leaf and a slice of ham. Arrange the buffers on plates and garnish with pesto