1 1/2 cups cold mashed potatoes
3 green onions, finely chopped
1 egg
1 tablespoon Dijon mustard
1/2 teaspoon dried dill weed
1/2 teaspoon salt
1/2 teaspoon ground black pepper
1 1/2 cups panko bread crumbs, divided
1/2 cup vegetable oil for frying, or as needed
Mix ham, mashed potatoes, green onions, egg, Dijon mustard, dill weed, salt, black pepper, and 1/4 cup panko bread crumbs together in a bowl until thoroughly combined. If mixture is too moist to hold together, mix in an additional 1/4 cup of crumbs. Place remaining panko crumbs into a shallow bowl. Scoop about 1/3 cup of the mixture and form into a ball; slightly flatten into a patty. Press both sides of patty into the panko crumbs; tap off any loose crumbs. Repeat with remaining mixture. Heat vegetable oil in a skillet over medium heat until very hot; pan-fry 2 or 3 patties at a time in the hot oil until golden brown on each side, 3 to 4 minutes per side.