Let the ham sit at room temperature for 1-2 hours. Trim any excess fat thicker than ¼ inch, then score the fat in a crosshatch pattern, being careful not to cut into the meat.

Preheat the oven to 325°F.

Line a roasting pan with foil and place a baking rack on top. Set the ham flat side down on the rack, pour about ½ inch of water into the pan, cover tightly with foil, and bake for 1 ½ to 2 hours, or until the internal temperature reaches 130°F (about 10 minutes per pound).

In a small bowl, mix the whole grain mustard, Dijon mustard, honey, and brown sugar until smooth. In another bowl, combine the panko, parsley, and olive oil.

Remove the ham from the oven and increase the temperature to 425°F.

Spread the mustard mixture evenly over the ham, reserving any extra for serving. Press the breadcrumb mixture on top to coat. Add more water to the pan if needed.

Return the ham to the oven, uncovered, and bake for 15-20 minutes, until the breadcrumbs are golden brown.

Let the ham rest for 10-15 minutes before slicing. Serve with any leftover mustard glaze.