Add shallots to skillet and sauté until translucent. Add garlic and sauté until caramelized. Stir in tomato sauce and banana catsup and simmer until slightly reduced, about 10 minutes. Add half the potatoes (or the trimmings if potatoes were cut tourne), and salt and pepper to taste. Add chicken, cover and simmer 30 minutes. Add chicken stock. Adjust taste using fish sauce or salt. Stir to mash potato pieces to thicken sauce. Stir in pepper pieces, pineapple and pickles. Stir in reserved liquid from pineapple, if needed, to thin the sauce.