Slice brown onion thinly. Cut carrot into 2" long match sticks. Slice green onion diagonally. Mix potato starch and water in a small bowl. Set aside.

Cook Udon in boiling water for a few minutes or to a preferred doneness. Set aside.

Heat Dashi in a pot at medium heat to just starting to boil, turn down to low heat, and add Soy Sauce, Sake, Mirin. Add brown onion and carrot, and cook until tender, then add beef. After beef turns color, skim the fat and scum from the surface of the soup. Add curry sauce mix, and stir until curry mix is dissolved.

Add potato starch slurry to the soup and stir well. When the curry soup has thickened, add Udon to the soup, and cook until Udon gets warm.

Top with sliced green onion before serving.