Separate and wash the leaves. Drain, dry thoroughly, and tear into shreds. Toss the minced bacon in a hot pan until crisp, then drain on soft kitchen paper.
Add the lemon juice, sugar, salt and mustard to the bacon fat remaining in the frying pan. Heat for 2-3 minutes, or until the sugar is dissolved. Arrange the lettuce leaves in a salad bowl, pour the hot dressing over, and toss gently.
Serve immediately, topped with the crumbled bacon.