1. Heat broiler.
2. Spread slices of bacon out on a work surface. Slice each cherry tomato in half. In center of one slice of bacon, place 1 cube of bread, 1 to 2 pieces of scallion and half a cherry tomato. Wrap bacon around filling, overlapping ends of the bacon tightly. Secure the bacon to the tomato and bread with a wooden pick. Repeat with remaining ingredients.
3. Broil the bacon packets 4 inches from the source of heat for 8 minutes, turning once.
4. Mix together the mayonnaise and mustard in small bowl. Let BLTs cool slightly. Remove wooden picks, if desired. Serve warm with the seasoned mayonnaise on the side for dipping. Makes 12 servings.