• Place potatoes in a large pot and pour in enough water to cover them by 2 inches; season with sea salt. Bring to a boil over medium-high heat.
• Reduce the heat and simmer until a paring knife slides easily through potatoes, 30-40 minutes.
• Drain and let cool slightly.
• Preheat the oven to 425 degrees.
• Whisk together the cream, sour cream, butter, egg yolks, and garlic in a large bowl. Season generously with salt and freshly cracked pepper, to taste.
• Peel the cooled potatoes and pass the flesh through a ricer directly into a large bowl.
• Pour in the cream/egg mixture. Fold in gently (be careful not to overmix).
• Transfer to an 8-inch baking dish and decoratively scrape or swirl the top with the tines of a fork to allow browning and texture.
• Bake uncovered, rotating once, until golden brown and slightly puffed, 30–40 minutes.

Making Ahead of Time:

• You can prepare this casserole 24 hours before serving.
• Follow the directions up until the baking step.
• Wrap the baking dish tightly with plastic wrap and place it in the refrigerator.
• Bake uncovered at 425 degrees for 45-50 minutes, or until golden brown on top.