How to Make It
Stir together ground beef, sake, soy sauce, dashi, and sugar in a small Dutch oven or medium-size, heavy saucepan. Cook over medium-high, stirring often to break up large lumps of beef, 5 minutes. Stir in peas and ginger; cook, stirring occasionally, until liquid is mostly evaporated and beef is no longer pink but is still moist, about 4 minutes. Remove from heat.
Divide rice evenly among 4 large bowls. Spoon 1/2 cup beef mixture over each. Garnish with pickled ginger.