Heat the sesame oil in a thick-bottomed pan.
Saute the sliced onion in the oil until translucent.
Add the beef slices to the onion and cook, tossing occasionally, until no longer pink.
Pour in the dashi, soy sauce, sake and mirin. Stir in the sugar. Bring to the boil, and allow to boil uncovered for five minutes.
Lower the heat and cover the pan. Simmer the beef until tender. If the liquid dries out before the beef is done, pour in water, no more than half a cup each time.
When the beef is tender, add the potatoes, carrot, shiitake and shirataki to the beef. Continue simmering until the carrot is tender (by that time, the potatoes and shiitake will be done too).
Spread the snow peas on the stew. Cover the pan. Simmer for five minutes.
Taste the stew. Add more soy sauce or sugar, or both, to balance the flavors.
Divide the beef, potatoes, carrot, shiitake, shirataki and snow peas among four bowls. Ladle in the sauce and serve hot.