Preheat the oven to 400°F. Grease a 9x9-inch baking dish with 1 tablespoon of the butter.

Peel the potatoes and slice them very thin, about ⅛ inch thick. Pat the slices dry with paper towels and set aside.

In a medium saucepan over medium heat, combine the heavy cream, minced garlic, salt, black pepper, and onion powder. Heat until just simmering around the edges. Remove from heat.

Layer half of the potato slices in the greased baking dish, slightly overlapping each slice. Pour half of the cream mixture evenly over the potatoes. Sprinkle with ¾ cup of the cheddar cheese and all of the Gruyere.

Layer the remaining potato slices on top in overlapping layers. Pour the remaining cream mixture evenly over the top.

Dot the top with the remaining tablespoon of butter cut into small pieces. Cover the dish tightly with aluminum foil.

Bake covered for 45 minutes.

Remove the foil. Sprinkle the remaining ¾ cup of cheddar and the smoked paprika over the top.

Bake uncovered for 20 to 25 minutes until the top is golden brown and bubbly and the potatoes are completely fork-tender.

Let the dish rest for 10 minutes before serving. Garnish with fresh chives.