Heat oil in a large wide pot on medium high. Add onion and garlic stir til fragrant.
Add the beef and curry roux. Stir until well browned.
Add the stock into the pot, turn up the heat to bring to a boil and then reduce to a simmer.
Add the carrots, soy sauce, and mirin. Cover and let simmer on medium low heat. Meanwhile, in another pot, cook the udon as per package instructions. Drain and set aside.
Once the carrots have slightly softened, add the swiss chard and kabocha. The more you stir, the thicker it will get from the kabocha, so if you want it to be soupier then do not stir as much, or add more water/stock as needed.
When veggies have all cooked through, add the udon and green onions. You can also leave the udon and curry seperated and add them together when serving. Taste and adjust seasoning as needed (soy sauce/mirin/salt).
Enjoy!