Slice each chicken breast in half crosswise to make 4 fillets (or use 5–6 boneless thighs). Cover with plastic wrap and pound to even thickness if needed; pat dry.
In a shallow dish, whisk together the 2 tablespoons flour, paprika, garlic powder, onion powder, cumin, salt, black pepper, and chipotle powder. Reserve 1 tablespoon of this flour mixture for the sauce.
Dredge each chicken piece in the remaining flour mixture, shaking off excess, and set on a plate or tray.
Heat 2 tablespoons butter and 2 tablespoons olive oil in a large skillet over medium-high heat until hot. Add the chicken and cook 4–5 minutes per side, depending on thickness, until golden and cooked through. Transfer chicken to a plate; do not wipe out the skillet.
In a small bowl, whisk the chicken broth with the cornstarch until smooth. Add the reserved tablespoon of flour mixture, brown sugar, soy sauce, lemon juice, and Dijon mustard to the skillet.
Bring the sauce to a simmer, scraping up browned bits from the pan. Simmer, stirring often, until the sauce thickens to the desired consistency; taste and add more lemon juice if you want it tangier.
Return the chicken to the skillet and spoon sauce over the pieces. Warm over low heat for a few minutes so the chicken soaks up some sauce.
Garnish with fresh parsley if desired and serve with mashed potatoes, polenta, rice, or cauliflower rice.