Cut the onions into slices and brown them thoroughly in a pot until they are all brown and reduced in volume. Cut the chicken into chunks and add it to the onions. When the chicken is cooked add 1l water. Also add the carrots and potatoes cut into bite-sized pieces. Add hondashi powder (I used one pack) and garlic cut into small pieces. Bring the mixture to a boil and simmer for 40 minutes. (Note that the potatoes will probably “decay” – so if you want them in chunks consider adding them later.)
Then add the Japanese curry roux, the soy sauce and the garam masala powder (to taste). Puree the bananas with a blender and add them as well. Simmer for another 10 minutes.
Serve the curry over steamed rice. (It is generally even better when warmed up the next day.)