Thinly slice the onion, cut the carrots into thick rounds, and cut the potatoes into cubes, then set them to the side.
Heat a pot over medium-high heat with a bit of oil. Add the cubed chicken thighs and brown for about 4 minutes, then remove from the heat and set aside.
In the same pot, add the sliced onions along with the garlic and ginger, and cook until the onions are slightly softened. Add the water, potatoes, and carrots, then cover and simmer for 10 minutes.
Add the chicken back in and bring everything to a simmer. Add the curry roux cubes and mix until they're fully dissolved.
Season the stew with the light soy sauce, Worcestershire sauce, ketchup, and sugar, and mix until the stew reaches your desired thickness.
Spoon into a bowl and optionally garnish with heavy cream, scallions, and some dried peppers. But it's your food, you eat it how you like.