Sprinkle two sticks of butter with 1 teaspoon of flour.
Pound the butter with a rolling pin (a French one without handles or a spinner). Flour your rolling pin if necessary.
Use a pastry scraper to gather up the butter again. Avoid handling it with your hand, because that will soften the butter.
Keep sprinkling 1 teaspoon of flour, pounding, and gathering butter until the butter is pliable and doesn’t break when you fold it over.
Shape the butter into a 4x4-inch square, wrap in plastic, and refrigerate for at least 10 minutes.