Cook your udon noodles in boiling water according to the package, then drain and set aside.
Dissolve the hondashi in 8 cups of water and set aside.
In a pot over medium heat, add a little oil and sauté the onions until soft.
Add the thinly sliced beef and cook it through.
Pour in the dashi stock, mirin, soy sauce, and sugar. Let it come to a boil.
Place your curry cubes in a strainer and submerge it in the broth, letting them dissolve completely.
Slowly stream in your beaten eggs while stirring gently, then lower the heat.
Plate your noodles, pour over the curry broth with beef and egg, and top with chopped green onions.