In a large wok or pan, heat on a medium high heat, pour in the oil and cook the onion and garlic until soft. Stir together ground beef, sake, soy sauce, dashi, Cook over medium-high, stirring often to break up large lumps of beef, 5 minutes. 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 and the greens of your choice, enjoy!