Prepare two large baking sheets by lining them with parchment paper. On each piece of parchment paper, trace six 4- to 5-inch circles with a pencil. Flip the parchment paper over so that the meringue will not be sitting directly on the pencil marks.
Pour 8 large egg whites into a very clean, large bowl or the bowl of a mixer. With a hand or stand mixer fitted with the whisk attachment, beat at low speed until the egg whites are foamy. Increase speed to medium and gradually pour in 2 cups sugar. Continue beating until the egg whites form stiff peaks when you lift the beaters out of the egg mixture. You now have a meringue. Take care not to overbeat the egg whites, as they can become grainy and dry.
Using a rubber spatula, gently transfer the meringue to a clean pastry bag fitted with a large circular or star tip, depending on the look you want to achieve.
Starting at the center of each circle, pipe a circle of meringue. When you reach the outer rim of the circle, pipe 1 to 2 additional layers on top of the border. The more you pipe, the deeper each shell will be.
Put the baking sheets in the oven. Bake for 1 1/2 hours, then turn off the oven and leave the meringues in the oven for 30 additional minutes.
Gently peel the meringues off of the parchment. Cool completely and put the meringues in an airtight container.
Freeze the meringues if you will not be using them in the next 3 to 4 days.