01 - Place eggs in a saucepan and cover with cold water. Bring to a rolling boil over high heat, then reduce to a gentle simmer and cook for 9 minutes. Transfer eggs immediately to an ice bath to cool. Once cooled, peel and roughly chop the eggs.
02 - While the eggs cook, lay bacon slices in a cold skillet. Set heat to medium and cook, turning occasionally, until evenly browned and crisp, about 6 to 8 minutes. Drain on paper towels, then crumble into small pieces once cool enough to handle.
03 - In a medium mixing bowl, combine the chopped eggs, mayonnaise, Dijon mustard, halved cherry tomatoes, crumbled bacon, and chives if using. Fold gently until evenly coated. Season with salt and freshly ground pepper to taste.
04 - Spoon the egg salad mixture evenly into the center of each butter lettuce leaf, dividing it among all 8 leaves.
05 - Fold or roll each lettuce leaf around the filling and serve immediately while the lettuce is crisp and the flavors are fresh.