How to Make It
Preheat oven to 450°F and preheat grill to medium. Combine egg yolk, lemon juice, and mustard in a medium bowl. Combine oils together in a measuring cup and very slowly drizzle into egg mixture, whisking constantly. As oils begin to emulsify, drizzle more quickly. Mash garlic to a paste with a pinch of salt and the edge of a chef’s knife. Add garlic paste, lemon zest, chives, and remaining salt. Chill in the fridge until ready to use.
Bake bacon in preheated oven on a rack-lined rimmed baking sheet until half-cooked and still malleable, about 10 minutes. Remove from oven and let cool until cool enough to handle, about 5 minutes. (Another method: Alternate indirect method: Grill on indirect heat until bacon is mostly crisp, about 12 minutes. Transfer to the direct heat and grill until bread is toasted and bacon is charred, about 2 minutes). Thread bacon around tomatoes and bread cubes on a skewer. Spray with cooking spray and sprinkle with black pepper. Place and grill and cook, covered, until bacon is crisp, tomatoes have burst, and bread is toasted, about 4 minutes per side. Transfer to a platter.
Spray romaine hearts with cooking spray and place cut-side down on direct heat; grill until lightly charred, 1 to 2 minutes. Serve skewers with grilled lettuce with smear/drizzle of aioli.