Heat oven to 350 degrees F. Place bread slices on a sheet pan and brush with olive oil on both sides. Sprinkle with salt. Bake in the oven for 7-8 minutes, turning bread over halfway, until golden and crisp. Gently rub toasted bread with garlic clove, set aside.
Place chicken between 2 sheets of plastic wrap or parchment paper. Using a rolling pin, lightly pound chicken to 1/4-inch thickness. Sprinkle chicken with salt and pepper. Combine 1 tablespoon butter and 2 tablespoons flour, set aside. Dredge chicken in the remaining flour to coat; shake off excess.
Heat a heavy large skillet over medium-high heat, add 2 tablespoons olive oil and 2 tablespoons butter. Without crowding the pan, add chicken to skillet, work in batches if necessary. Cook chicken until golden brown and cooked through, about 3 minutes per side. Transfer chicken to platter; tent with foil to keep warm.
Add wine, lemon juice, and broth to the skillet, scraping all the brown bits left in the pan. Boil in skillet over medium-high heat. Add butter-flour mixture and whisk until well combined. Bring to a boil and continue whisking until sauce thickens slightly, about 2 minutes. Stir in capers, parsley and remaining 1 tablespoon butter. Season sauce to taste with salt and pepper.
In a bowl combine arugula, apples, and shallot. Drizzle with olive oil and lemon juice. Toss until well combined. Place arugula on toasted bread, top with chicken, shaved parmesan, parsley and sauce.
Recipe adapted from: https://thenoshery.com/open-faced-chicken-picatta-sandwich