01 - Place eggs in a saucepan and cover with cold water by 1 inch. Bring to a rolling boil over medium-high heat, then reduce to a gentle simmer and cook for 9 minutes. Transfer eggs immediately to an ice bath and let cool for 5 minutes before peeling. Roughly chop the peeled eggs and set aside.
02 - While the eggs cook, lay bacon slices in a cold skillet. Turn heat to medium and cook, turning occasionally, until evenly browned and crispy, 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 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 bacon is still crisp.