In a small bowl, combine the first 9 ingredients. Place chicken in a 6-qt. electric pressure cooker; pour broth mixture over meat. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 10 minutes. Allow pressure to naturally release for 10 minutes, then quick-release any remaining pressure.
Remove chicken; keep warm. Skim fat from cooking liquid. In a small saucepan, melt butter; whisk in flour until smooth. Gradually add cooking liquid. Cook and stir until sauce is thickened, 2-3 minutes. Serve with chicken.