Heat 6 cup water on a pressure cooker. Add chicken gizzard. cover and pressure cook for 15 minutes. Note: Start the timer once the pressure regulator moves. You can also boil in a regular pot for 45 minutes.
Remove the gizzard from the pressure cooker. Drain the water. Chop into small pieces and set aside.
Meanwhile, boil 6 cups water on a regular pot. Add chicken heart. Boil for 15 minutes. Remove from the pot and chop into small pieces.
Make annatto oil by heating oil in a saucepan. Add annatto seeds. Cook in low heat until the oil turns red.
Heat a cooking pot and pour annatto oil. Note: use a kitchen strainer to filter the seeds.
Saute onion, garlic, ginger, and tomato.
Add the chopped chicken gizzard. Cook for 1 to 2 minutes.
Add chicken heart. Cook for 2 minutes.
Add chili pepper and bay leaves.
Pour soy sauce into the pot. Stir.
Pour water. Let boil. Cover and cook for 15 minutes.
Add vinegar. Let the mixture re-boil. Stir and continue to cook for 5 minutes.
Add carrots, daikon radish, and red bell pepper. Stir. Cook for 3 minutes.
Season with fish sauce and ground black pepper.
Transfer to a serving bowl. Serve.