Preheat the oven to 350 degrees. Grease a 3-quart baking dish.
Stir together whipping cream, yogurt, curry paste, and honey; pour half into the dish.
Arrange ham, potatoes, and leek in an overlapping layer, then top with remaining whipping cream mixture. Sprinkle with salt, 1/2 teaspoon pepper, and cheese.
Bake, covered with aluminum foil, for 40 minutes. Uncover and continue baking until potatoes are tender and top is golden brown, about 20 minutes more. Let stand for 15 minutes. Garnish with remaining black pepper and green onion.