Mix the crabmeat with mayonnaise, mustard, lemon juice, salt and black pepper to taste. You may chill for a few minutes or let it stay on the fridge for not more than one day.
Take a small, pretty lettuce leaf and press it into the centre of the cup.
Once all the cups are made, put a spoonful of the crab mousse into each. Press down firmly with a fork but don't whack hard.
Place on a plate and add extra lemon juice where needed.
Serving Suggestions: Serve on a platter with some chips and lemon for squeezing.