Adjust the oven rack so it is 6 inches from the broiler element. Heat the broiler on high. Put the bread on a baking tray and toss with ¼ cup of the olive oil and ¼ tsp. salt. Broil, turning every minute, until evenly browned and crisp, about 3 minutes total. Set aside to cool

Put the anchovies, garlic, egg yolk, lemon juice, zest, Worcestershire sauce, ¼ tsp. salt, and 1/8 tsp. pepper in a tall container that fits a hand-held immersion blender (a 2-cup liquid measure works well). Use an immersion blender to purée the ingredients. With the blender running, slowly add the remaining ½ cup olive oil to form a thick dressing. Add ¼ cup of the Parmigiano-Reggiano and blend to mix.

Put the lettuce in a large bowl and toss with the dressing and freshly ground black pepper to taste. Add the remaining ¼ cup Parmigiano-Reggiano and the bread cubes, toss, and serve immediately.