1. Whisk broth, vinegar, marmalade, mustard and cornstarch in a medium bowl.

Sprinkle chicken with salt and pepper. Heat 2/3 teaspoons oil in a large skillet over medium-high heat. Add the chicken and cook until golden, about 2 minutes per side. Transfer to a plate and cover with foil to keep warm.

Add the remaining 1/3 teaspoons oil and shallots to the pan and cook, stirring often, until beginning to brown, about 30 seconds. Whisk the broth mixture and add it to the pan. Bring to a simmer, scraping up any browned bits. Reduce heat to maintain a simmer; cook until the sauce is slightly reduced and thickened, 30 seconds to 2 minutes. Add the chicken; return to a simmer. Cook, turning once, until the chicken is heated through, about 1 minute. Remove from the heat and stir in orange zest.