To a large pot over medium-high heat, combine your broth, hondashi, soy sauce, mirin, and curry roux. Stir until completely combined and allow to come to a simmer.
Add your onions and allow to cook on simmer for about 8-10 minutes.
Add the udon and thinly sliced beef and allow to cook until udon is cooked all the way through, being careful not to overcook (since I used frozen udon, I just wait till the noodles separate and then immediately take off heat).
