Fire up. Prepare a grill for 2-zone cooking by placing a chimney full of pre-heated charcoal briquets on one side of the grill’s charcoal grate in order to create direct and indirect cooking zones. Open the grill vents fully for high heat cooking (a.k.a. Warp 10) on the indirect side, at least 450°F (232°C). On a gas grill, adjust the temperature knobs so that one half of the grill is off and the other half is as hot as possible.
Cook. Combine the brown sugar, balsamic vinegar, butter, and Dijon mustard in a small saucepan. Place the saucepan on the hot side of the grill and heat until the sugar has melted and the mixture is smooth, approximately 4 minutes. Move the glaze to the cool side of the grill to keep warm.
Grill the ham steak on the hot side of the grill until lightly charred, approximately 2 to 3 minutes per side. Brush the top of the ham steak with the glaze and flip to set the glaze over direct heat, approximately 20 seconds. Repeat with the other side of the ham steak so that it is completely glazed. Brush both sides of the ham steak again with glaze and move it to the indirect side of the grill until ready to serve.
Serve. Remove the glazed ham steak from the grill, plate, and serve immediately.
