01 - Place eggs in a saucepan, covering them with cold water by one inch. Bring to a rolling boil over high heat. Reduce heat and simmer gently for 9 minutes. Transfer eggs to a bowl of ice water and allow to cool completely.
02 - Once cooled, peel eggs carefully and chop into medium pieces for optimal texture.
03 - While eggs are cooling, cook bacon in a skillet over medium heat until crisp. Remove and drain slices on paper towels. When cool, crumble bacon into small pieces.
04 - In a medium mixing bowl, combine chopped eggs, mayonnaise, Dijon mustard, cherry tomatoes, crumbled bacon, and fresh chives if using. Season the mixture with salt and black pepper to taste, mixing until evenly coated.
05 - Arrange butter lettuce or romaine leaves on a serving platter. Spoon even portions of egg salad mixture into the center of each leaf.
06 - Fold or gently roll each lettuce leaf around the filling. Serve immediately while crisp.