Add oil into a pot and heat over medium high heat.
Add onion and sauté for a few minutes or until the onion becomes translucent and edges start getting slightly burnt.
Add potatoes and carrots into the pot; stir for a couple of minutes or until the surface of the vegetables starts getting cooked.
Add water and turn the heat up to bring it to a boil; then reduce the heat to medium low and simmer for about 7 minutes or until the vegetables are nearly cooked through
Break the curry roux cake into small blocks, along the lines, and add them into the pot; stir gently to blend the curry roux.
Reduce the heat to low, place a lid on and cook for about 10 minutes or until the curry roux is completely dissolved; stir occasionally as the curry tends to stick to the bottom of the pot.
Check the consistency of the sauce; it should be like béchamel sauce – If it's too thick, adjust with some water; if too thin, cook further without the lid; it will thicken when cooled down as well.
Place a cup of hot cooked rice onto one side of a plate; place the chicken cutlet pieces next to the rice, leaning them on the rice so that there will be a space to pour the curry.
Pour curry next to the chicken cutlet; put the Japanese pickled vegetables (fukujinzuke) on the side; serve immediately.
