Sinigang na Baboy (Pork in Sour Broth)

While the pre-prepared sinigang mixes (Knorr and Mama Sita) I've used contain tamarind, I use lemon juice and patis (fish sauce) when cooking from scratch. This recipe is modified from Filipino Cooking Here and Abroad.

NOTE: The original recipe calls for 5-6 pieces of tamarind to be added along with the tomatoes and onion. Then it should be removed, mashed with some of the broth, and the resulting liquid should be returned to the pot. Lemon juice is one substitute; another is 2-3 stalks of rhubarb - I've never tried this, but assume that some adjustment would be necessary.

• 2-1/2 lb. baby back ribs, cut into pieces
  
• 10 cups water
• 4-5 medium tomatoes, sliced (I use Roma)
• 1 large onion, sliced
  
• 4-6 tbsp. patis
  
• 4-6 tbsp. lemon juice
  
• 1 lb. green beans, trimmed
  
• 5 oz. spinach, chopped
• 2-4 baby bok choy, chopped - separate leaves and stems (optional but yummy)
  

Bring water and pork to a boil. Add tomatoes and onions. Simmer covered for 1 hour, or until tender.

Add lemon juice and patis. Taste and correct seasoning.

Bring to a boil, then add green beans and baby bok choy stems. Cook for 5-8 minutes more, or until beans have reached desired texture.

Add spinach and bok choy leaves, cover and remove from heat. Let stand 5 minutes.