Soak the tiger nuts in water for 24 hours, changing the water every 8 hours.

Drain and rinse the tiger nuts.

Weigh the tiger nuts and blend them in a blender with an equal amount of cold water until you get a thick, slightly liquid paste.

Cover the paste with plastic wrap and let it rest in the refrigerator for 2 hours.

Mix the paste with the remaining cold water.

Strain the mixture through a fine mesh strainer, pressing the blended tiger nuts with a wooden spoon to extract all the liquid.

Mix the horchata with the powdered sugar and strain it again through a fine cloth or very fine mesh strainer to remove any remaining impurities.

Chill the horchata in the refrigerator in a wide glass pitcher and stir just before serving to mix in any powdered sugar that may have settled at the bottom.