Preheat the oven to 375°F and position the rack just above the center. Lightly butter a standard pie plate to prevent sticking.
Melt 1 1/2 tablespoons of butter in a medium skillet over medium-high heat. Add the chopped onion and sauté for 4 minutes until the edges are golden. Reduce the heat to medium, add the minced garlic, and cook for 2–3 minutes until fragrant but not browned.
In a medium mixing bowl, combine the cooked onion and garlic, corn kernels, milk, 1 1/2 cups of cheese, 1/2 cup of panko, salt, white pepper, and 2 1/2 tablespoons of chives if using. Mix thoroughly, then add the eggs and stir to blend well.
Pour the corn mixture into the prepared pie plate, smoothing the surface evenly.
Melt the remaining 1/2 tablespoon of butter and allow to cool slightly. In a bowl, mix it with 1/4 cup of panko, 1/2 cup of cheese, 1/2 tablespoon of chives, and a pinch of salt and pepper. Sprinkle this mixture evenly over the pie filling.
Place the pie plate on a rimmed baking sheet for stability. Bake for about 35 minutes until puffed, set, and lightly browned. Cool for 5–10 minutes before serving. Garnish with paprika and extra chives if desired.