Toss potatoes, and 1 tablespoons oil in microwave safe bowl. Cover with plastic wrap and microwave on high power until tender, 4-5 minutes, tossing potatoes halfway through cooking.
Place flour in shallow dish. Season chicken with salt and pepper, dredge in flour, and shake to remove excess. Melt 1 tablespoons butter with remaining 2 tablespoons oil in large skillet over medium-high heat. When foam subsides, cook chicken until browned on both sides, 3-5 minutes per side. Transfer to plate, leaving fat in skillet, and cover chicken with foil.
Reduce heat to medium, add potatoes, cut side down, and cook until browned, 4-5 minutes. Transfer to platter. Add broth, sage and lemon juice and, using wooden spoon, scrape browned bits from skillet. Return chicken and accumulated juices to pan and simmer until sauce is slightly thickened and chicken is cooked through, about 5 minutes. Transfer chicken to platter with potatoes. Whisk remaining tablespoon butter into sauce, season with salt and pepper, and pour over chicken and potatoes. Serve.