In a small saucepan, bring the apple cider to boil and cook until reduced by half (1 cup). Remove the saucepan from heat and stir in honey and Dijon mustard. Set aside 1/2 cup for serving.
Brush remaining glaze onto chicken, pork, or Cornish game hens during the final 30 minutes of roasting, basting with pan juices occasionally (cover with foil if anything starts to brown too quickly).
Remove hens from oven, tent with foil, and let stand 10 minutes. Serve with reserved apple glaze.
Apple cider or juice: You can make your own cider in about 3 hours, or find it at the store at certain times of the year. Apple juice works too!
Honey: Or sweeten with sugar or maple syrup to taste.
Yield: This recipe makes about 1 cup glaze (technically 1 cup + 2 tablespoons). It's enough to handily glaze 2 chickens, a large turkey, or 4 Cornish hens (or reserve some sauce for passing separately).
Storage: Store leftovers covered in the refrigerator for up to 4 days.
Make ahead: Prepare the glaze a day in advance and store covered in the refrigerator. Bring to room temperature before basting or reheat any reserved sauce on the stove before passing separately.