Cut the bacon into very small pieces and place in a cold frying pan. Cook over medium heat, stirring occasionally, until crispy. Drain on paper towels.

Peel the eggs and cut in half lengthwise. Place the yolks in a mixing bowl and smash with a fork until fairly smooth. Add the mayonnaise and mustard and mash together. Finely chop the egg whites and add to the yolk mixture. Reserve a little of the bacon and tomato to garnish and stir the rest into the dip. Season to taste with salt and pepper. Refrigerate until serving. Garnish with the reserved bacon and tomato and serve with small lettuce leaves.