Preheat a medium pot over medium heat. When hot, add 1 tbsp oil and add the onion slices.
Sauté the onion slices for 2-3 minutes. Add carrots (optional) and sauté for another 2 minutes. Add sliced meat.
Cook the meat for a minute or until barely pink. Add 2 tbsp sake or mirin.
Add dashi stock to the pot and cover with lid. Reduce heat to medium low and cook for 5 minutes. Skim off scum if needed.
Cook udon noodles as per packaging directions. If frozen, blanch in boiling water for a max of 1 minute for chewy texture.
Dissolve the curry cubes completely in a ladle before adding to the soup.
Add 2 tsp soy sauce and mix well. Turn off heat and cover with lid to keep warm.
Drain the noodles. Pour curry soup over udon noodles. Top with green onions and serve.
