How to Make It
Preheat the oven to 375°. Line a baking sheet with a wire rack. In a food processor, pulse the chopped bacon with the garlic cloves until minced. Add the bread crumbs, Parmesan, milk, egg, thyme, rosemary and hot sauce, season generously with salt and pepper and process to a paste. Transfer the paste to a medium bowl and knead in the ground sirloin.
Preheat a griddle or grill pan. Spread the meat mixture evenly on 4 slices of the white bread. Top with another 4 slices of bread and brush both sides of the sandwiches with olive oil. Brush the remaining 4 slices of white bread lightly with olive oil and set aside. Place the sandwiches on the griddle and top with a heavy skillet. Cook over moderate heat, turning the sandwiches once, until they are golden, about 6 minutes total. Transfer the sandwiches to the rack and bake until the meat is cooked through, about 8 minutes longer.
Meanwhile, in a medium skillet, cook the remaining 8 slices of bacon until crisp, about 6 minutes. Drain on paper towels. Toast the remaining 4 slices of white bread on the griddle until golden, about 2 minutes per side.
In a small bowl, blend the mayonnaise with the chopped chipotle chile. Spread the mayonnaise on the meatloaf sandwiches and top with the bacon, tomatoes, lettuce and toasted bread. Cut each sandwich in half. Secure each half with a toothpick and serve with cornichons and mustard.