INGREDIENTS
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1 tablespoon unsalted butter, at room temperature, for greasing the baking dish
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1 tablespoon unsalted butter, at room temperature
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2 teaspoons kosher salt, plus extra for seasoning
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4 pounds russet potatoes, peeled, cut into 1-inch pieces
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1 1/2 cups grated mozzarella
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1 cup whole milk, at room temperature
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3/4 cup freshly grated Parmesan
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1/2 cup (1 stick) unsalted butter, melted
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Freshly ground black pepper
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2 tablespoons unsalted butter, at room temperature
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2 cups frozen peas, thawed
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1/2 teaspoon kosher salt
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1/4 teaspoon freshly ground black pepper
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1/2 cup freshly grated Parmesan
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2 tablespoons plain dry breadcrumbs
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Extra-virgin olive oil, for drizzling