Old-Fashioned Sweet Potato Pie

INGREDIENTS

• 3 egg whites
• 1 cup milk
• 1/4 teaspoon salt
• 1/4 teaspoon ground cinnamon
• 1/4 teaspoon ground ginger
• 2 eggs
• 2 cups peeled, cooked sweet potatoes
• 1 1/4 cups sugar
• 1 teaspoon vanilla extract or 1 to 2 tablespoons bourbon
• 1/2 stick melted butter
• 9-inch unbaked pie crust