Step 1

Place a rack in middle of oven; preheat to 350°F. Spread out torn bread on a rimmed baking sheet. Set a wire rack in baking sheet over bread and arrange bacon on rack (it’s okay if strips overlap a bit; they’ll shrink as they cook). This setup will crisp the bacon, and as the bread becomes enriched with some of the drippings, it will get nice and toasty. Bake 20 minutes. Remove from oven and turn bacon. Carefully tilt baking sheet to pour off any fat into a small bowl; reserve for another use if desired. Return to oven and bake until bacon is brown and crisp and breadcrumbs are golden brown, about 20 minutes more. Transfer bacon and toasted breadcrumbs to separate paper towels to drain.

Step 2

Slide breadcrumbs, still on paper towels, to a cutting board and crush into very small pieces with a flat-bottomed measuring cup. Season with salt, place on a small plate or in a small bowl, and set aside for serving.

Step 3

Meanwhile, whisk mayonnaise, lemon zest, lemon juice, horseradish, pepper, and 1/2 tsp. salt in a small bowl to combine; set aside.

Step 4

Arrange bacon, lettuce leaves, tomatoes, basil, and lemon wedges on a platter or on a couple of plates and in bowls so that each component is visible and easily accessible. Set out kitchen shears next to bacon for cutting to size. Serve with breadcrumbs and reserved horseradish mayonnaise (for spreading over lettuce).