Peel potatoes, cut into 3/4-inch pieces (just eyeball it). You’ll have just over 6 cups chopped potatoes. Cover with water in a medium pot. Bring to boil. Once boiling, boil for just 5–6 minutes. You don’t want the potatoes super soft and tender just yet, only slightly softened. Drain.

Grease a 9×13-inch or any 3–4-quart oven-safe dish. Add warm drained potatoes, ham, and 1 cup (about 100g) of shredded cheese. Gently toss together. Set aside.

Preheat oven to 375°F (191°C).

Melt the butter in a large skillet or saucepan over medium heat. Add the onion and garlic and cook, stirring occasionally, until onions have softened, about 3 minutes. Stir in salt, pepper, smoked paprika, ground mustard, parsley, and flour until combined and flour has absorbed any liquid. Reduce heat to low, and then slowly stir in the milk. Simmer for 3–5 minutes or until thickened into a gravy consistency. Remove from heat. Taste and, if desired, add more salt, pepper, paprika, mustard, or parsley to taste.

Pour warm sauce over ham and potatoes. Toss gently to coat.

Bake, covered with aluminum foil, for 30 minutes. Remove aluminum foil, sprinkle remaining cheese on top, and return to the oven for 5–10 more minutes or until cheese is melted and casserole is bubbling around the edges.

Remove from the oven and garnish with fresh parsley, green onion, chives, or a drizzle of hot sauce.

Store leftovers in the refrigerator for up to 1 week. Reheat as desired. To reheat the entire casserole, cover with aluminum foil and reheat in a 350°F (177°C) oven for 20 minutes.