Season the pork ribs with the salt, sugar, ground pepper and garlic powder. Set aside.
Heat oil over medium-high heat in a cooking pot, and sauté the onions and garlic until fragrant, but not browned. Add the seasoned pork ribs and stir continuously. Once the ribs are no longer pink, add the tomato paste and continue stirring until the ribs are well coated. Pour in the hot water, add the bay leaves, lower the heat to medium-low and simmer covered for 20 minutes.
Taste the broth to see if it the salinity is adequate. If not, add some salt to taste. Then, add the carrots and continue to simmer covered for another 10 minutes. Add the potatoes and mushrooms and continue simmering covered for another 15 minutes. Finally, add the peas and fish sauce and bring to a gentle boil.
In a small bowl, thoroughly mix the corn starch with 1 tablespoon of water and stir into the ragu. Once it has come to a gentle boil, it is ready to serve. Garnish with ground black pepper and chopped cilantro.