Preheat the oven to 375 degrees F. Place the almond paste and sugar in a large mixing bowl. Beat with an electric mixer on medium-high speed until the almond paste is softened and the sugar well-incorporated, about 5 minutes.

Add the egg whites a little bit at a time, incorporating fully after each addition. Egg whites are difficult to pour in small amounts, so hold a rubber spatula against the rim of the bowl, and use it to "cut" the egg whites as they are poured. If you add the egg whites all at once, the mixture will be lumpy, because the difference in consistency between the egg whites and the almond paste mixture is too great. Using a rubber spatula, scrape down the sides of the bowl as needed. You may or may not need all of the egg whites depending on the moistness and age of the almond paste. Stop mixing when the mixture reaches a consistency soft enough to pipe (similar to toothpaste).

Place the batter in a pastry bag fitted with a 1/2-inch plain tip. Pipe 1-inch mounds onto a parchment-lined sheet pan. It will be easier if you hold the pastry bag at a slight angle and allow the tip to touch the parchment as you start to pipe. Once you have formed the mound, stop squeezing and lift the tip straight up, leaving a small tail on the top of each mound. Space the macaroons about 1-inch apart to allow for spreading and pipe carefully. The macaroons will look nicest when sandwiched together if they are all the same size.

Immediately before placing them in the oven, liberally sprinkle granulated sugar over the macaroons. This will give them a nice crust that will keep the inside moist and chewy. Bake until golden brown, 8 to 10 minutes. The top of each macaroon should be very finely cracked, a characteristic for which they are known. If over-baked, the macaroons will be dry and crunchy.

Remove the sheet pan from the oven and immediately pour the water onto the sheet pan under the parchment paper. Be careful! If you get any water on the macaroons, they will be soggy. You will need to tilt the baking sheet to spread the water evenly. Let it sit for 2 minutes. The water will loosen the macaroons from the paper. Remove the macaroons from the paper two at a time and stick them together, matching the flat sides. Do not put them back on the hot, wet baking sheet or they will become soggy.

The macaroons can be stored in an airtight container at room temperature for up to three days or well wrapped in the freezer for up to one week. Unwrap them before bringing back to room temperature, or the condensation will make them soggy.