Place chicken between 2 sheets of plastic wrap on work surface. Using mallet, pound chicken to 1/3-inch thickness. Sprinkle chicken with salt and pepper. Place 2 sage leaves atop each chicken breast half. Top each chicken breast with 2 prosciutto slices, pressing to adhere. Spread 1/2 cup flour on plate. Turn chicken in flour to lightly coat both sides.

Melt butter with oil in large nonstick skillet over medium-high heat. Add chicken, prosciutto side down; cook 4 minutes. Turn chicken over and cook just until cooked through, about 3 minutes. Transfer to platter and cover to keep warm; reserve skillet.

Whisk wine with remaining 2 teaspoons flour in small bowl. Add broth and lemon juice to same skillet; bring to boil. Add wine mixture; whisk until sauce thickens slightly, about 30 seconds. Season to taste with salt and pepper.