2 ounces Parmesan cheese, grated on a rasp-style grater (to make 1 cup)
1 cup panko bread crumbs
4 tablespoons unsalted butter, melted
6 tablespoons unsalted butter, not melted but cut into 6 pieces
2 ½ pounds russet potatoes, peeled and cut into 1-inch chunks
3 cups light cream (or heavy cream but do not use half-and-half)
⅛ teaspoon baking soda
- Adjust oven rack to middle position and heat oven to 375 degrees.
- Combine Parmesan, panko, melted butter, and 1/4 teaspoon salt in bowl; set aside.
- Bring potatoes, 2 ½ cups cream, baking soda, 2 teaspoons salt, and 1 teaspoon pepper to boil in large saucepan over medium-high heat. Reduce heat to low and cook at bare simmer, stirring often, until paring knife slides easily into potatoes without them crumbling, 20 to 25 minutes.
- Turn off heat. Stir remaining 1/2 cup cream and remaining 6 tablespoons butter into potato mixture until butter has melted, about 1 minute.
- Transfer potato mixture to 13 by 9-inch baking dish. Sprinkle Parmesan-panko mixture over top. Bake, uncovered, until bubbling around edges and surface is golden brown, 15 to 20 minutes.
Let cool for 15 minutes before serving.