Prep: Preheat grill to 450℉ (we will decrease it later). In an aluminum roasting pan, add 3 cups water, 2 yellow onions (sliced), 2-3 whole cloves, and 1-2 star anise. Set aside.
Make Glaze: Add Glaze ingredients to a small bowl; whisk to combine. Set aside.
Prep Ham: Place a 7-8 pound pre-cooked ham on a plate and use a paring knife to score the outer skin crisscross (be careful not to cut all the way down into the meat). Place ham on top of the onions in the aluminum pan (note: feel free to place a roasting rack inside as well, if the onions don't raise the ham off the bottom enough or some celery stalks will work too). Brush the ham with some of the glaze, saving most of it for later.
Grill: Place on the grill, uncovered, and close the grill lid to let it cook for 20 minutes. Open the lid quickly and cover the ham tightly with foil. Close the lid and drop temperature down to 325-350℉ and let it cook approximately 18-22 minutes per pound (include the first 20 minutes in the total cook time) or until it reaches an internal temperature of 135-140℉ (use a meat thermometer). Check occasionally to track the temp and add additional water if the liquid is cooking off quickly.
Glaze Ham: When there is approx. 10-20 minutes of cook time left, open the grill lid and remove the foil. Brush the entire ham liberally with the glaze, ensuring you get in every nook and cranny. Close the lid and increase the grill temperature to 400-425℉. The glaze should get a little tacky and start to caramelize.
Rest: Remove from grill (save liquid in the bottom for gravy, if making) and let rest 10-15 minutes. Feel free to brush on any remaining glaze.
Optional Ham Gravy: Bring cast iron skillet to medium-high heat. Add 3 tablespoons butter and let melt. Add in 3 tablespoons all-purpose flour and whisk together until it forms a paste (a.k.a. a roux). Slowly add 1 ¾ cups ham drippings/liquid approx. 1/4 cup at a time whisking constantly. Continue adding liquid until fully combined. Let simmer to thicken, add additional splashes of liquid to thin. Taste and add any salt or pepper, as desired.
Serve: Slice the ham and serve with gravy and any other delicious side dishes!
Notes
Cook Time: total cook time will vary depending upon the overall thickness of your ham, outdoor temp, wind, humidity, etc. Use a dependable internal meat thermometer to keep track of temp to determine when ham is fully heated through.
Storage: store leftovers in an airtight container in the refrigerator for up to 3 days.
Leftovers: if you use a bone-in ham definitely save it and make some Ham + Split Pea Soup!
Nutrition Info is calculated without the optional gravy.