Preheat the oven to 375°F.
Place the diced potatoes in a large pot of water. Bring the water to a boil and cook the potatoes until they are fork-tender, usually about 15-20 minutes.
Drain the potatoes and return them to the pot. Mash them with greek yogurt and milk until smooth and creamy. Set the mashed potatoes aside.
In a greased 9x13-inch baking dish, carefully spoon the mashed potatoes into an even layer.
Top the mashed potatoes with corn then bite-sized panko chicken pieces. Finally top all with shredded cheese.
Place the casserole in the oven and bake for about 20 minutes, or until the top is golden brown and the casserole is heated through.