Noodles should be cooked according to package instructions and divided between two bowls. Make the curry soup by frying the chopped onion in sesame oil for a few minutes. Add the curry powder, water and cornstarch mix, mirin, soy sauce, and dashi powder. Keep stirring until the soup begins to bubble and thicken. Turn the heat off and and ladle the curry soup into each bowl. Top with baby spinach and scallions and enjoy!