Classic Sweet Potato Casserole

Ingredients

• 5 pounds sweet potatoes peeled, about 4 sweet potatoes or five 16-ounce cans unseasoned mashed sweet potatoes
• 1 cup brown sugar packed
• 1/2 cup granulated sugar
• 1/2 cup half-and-half
• 4 ounces unsalted butter at room temperature, plus more for the baking dish
• 2 teaspoons vanilla extract
• 2 teaspoons sea salt ground, or kosher salt
• 1 1/2 teaspoons ground cinnamon
• 1 teaspoon ground ginger
• 1/2 teaspoon ground nutmeg
• 4 large eggs lightly beaten
• 4 cups mini marshmallows