In a large saucepan combine the amaranth and the water. Cover the pan and bring the mixture to a boil, whisking occasionally. Using a heatproof rubber spatula, push any seeds clinging to the side of the pot into the liquid then reduce the heat to low and continue to simmer, covered, until the liquid is absorbed, 20 to 25 minutes. Stir in salt.
Remove the pan from the heat and let it stand, covered, 5 to 10 minutes. Divide amaranth among bowls and top with nuts, honey, and milk.