Start by thoroughly cleaning the cow trotters (paa ng baka) under cold running water. Remove any excess hair or debris. For best results, soak them in vinegar water for 15 minutes to remove any gamey smell (malansa). Pat dry with paper towels.
While the trotters are soaking, prepare your ingredients: crush 5 cloves of garlic (dinurog na bawang), chop 1 onion into small pieces, crush 2 knobs of ginger (dinurog na luya), cut the white parts of lemongrass into 4-inch pieces, slice the bell pepper into strips, and cut green onions into 2-inch lengths.
In a large pot over high heat (220°C/430°F), combine the clean trotters with 10 cups of water, 1 teaspoon ground black pepper, and the prepared lemongrass. Bring to a rolling boil, then immediately reduce heat to low (120°C/250°F). Skim off any scum that rises to the surface (alisin ang bula).
Let the mixture simmer on low heat for 3 hours, checking occasionally and skimming when needed. The meat should become very tender and start to fall off the bone. Keep the pot partially covered and maintain the liquid level by adding hot water if necessary.
When you reach the 3-hour mark, heat 3 tablespoons of oil in a separate pan over medium heat (160°C/320°F). Sauté the crushed garlic until light golden, then add the chopped onions and ginger. Cook until the onions become translucent and fragrant. Set aside.
Remove the lemongrass pieces from the main pot. Add the sautéed aromatics, 2 teaspoons of annatto powder (atsuete), 3 tablespoons of salted black beans (tausi), and 1 Knorr beef cube to the simmering broth. Continue cooking for 30 minutes at low heat (120°C/250°F).
Add the sliced bell pepper, 3 jalapeño peppers, and cut green onions. Cook for another 10 minutes. Season with fish sauce (patis) to taste.
Do a final check - the meat should easily fall off the bone (dapat malambot na) and the broth should be rich and slightly thick. Test the seasoning and adjust if needed.
Turn off the heat and let the Balbacua rest for 5 minutes before serving. This allows the flavors to settle and the temperature to become perfect for eating.