Make dressing: Preheat oven to 425ºF with a rack in the center position. Finely grate Parmesan into a large bow. Peel and grate ½ teaspoon garlic into the same bowl. Juice lemon. Whisk in 1½ tablespoons lemon juice (reserve remaining juice for step 5). Whisk in Dijon, mayonnaise, and 1 tablespoon oil. Season to taste with salt and several grinds of pepper.

Make croutons: Cut ciabatta into 1-inch pieces. Spread in a single layer on a piece of foil, and bake on center oven rack until toasted, 6–8 minutes (watch closely).

Prep chicken: Beat 1 large egg in a shallow bowl; season with salt and pepper. In a second shallow bowl, combine ½ cup flour and ½ teaspoon salt. Pat chicken dry. Using a meat mallet or heavy skillet, pound chicken to ¼-inch thickness; season all over with salt and pepper.

Coat & cook chicken: Dip chicken in egg mixture, then press into the flour, tapping off excess. In a medium skillet heat ⅛ inch oil over medium-high. Add chicken and cook until golden brown and cooked through, 4–5 minutes per side. Transfer to a paper towel-lined plate.

Make sauce: Whisk ½ cup water, reserved lemon juice, broth concentrate, and 1 tablespoon butter into skillet, scraping up any browned bits. Season to taste with salt and pepper. Reduce heat to medium. Simmer until slightly reduced, about 2 minutes.

Finish salad & serve: Cut romaine crosswise into 1-inch pieces, discarding ends. Add romaine and croutons to the bowl with dressing, and toss well to combine. Add chicken back to the skillet, turning to coat with sauce, which will thicken slightly. Transfer to plates, spoon sauce on top, and serve salad alongside.