Slice the chicken breasts in the half through the equator to create 4 fillets. Cover with plastic wrap and pound to an even thickness. Pat dry.
Whisk the flour and all chicken seasoning together in a shallow dish. Reserve 1 tablespoon to use later in the sauce. Dredge each breast in the remaining flour mixture, shake off any excess, then transfer to a dry surface.
Melt the 2 tablespoons butter in 2 tablespoons oil in a large skillet over medium-high heat. Once hot, add chicken and cook for 4-5 (depending on thickness) per side until golden and cooked through. Transfer chicken to a plate, don't wipe out skillet.
Mix chicken broth with cornstarch and add to the skillet, followed by all of the sauce ingredients, including the 1 tablespoon reserved flour mixture. Bring sauce to a simmer while scraping up any brown bits on the bottom of the pan; simmer until sauce thickens to desired consistency, stirring often. Taste the sauce and add additional lemon juice for tangier/less sweet if desired.
Add chicken back to the skillet and spoon some of the sauce over top. Warm through over low heat so the chicken can soak up some of the sauce. Garnish with fresh parsley (optional) and serve with mashed potatoes, polenta, rice or cauliflower rice. If the chicken is too sweet for your liking, garnish with freshly squeezed lemon juice.