Braised pork ribs with yam

Ingredients

• 420 gm pork ribs, cut to 2 inch lengths
• 300 gm yam, peeled and sliced to 1/4 inch thick
• 5 pips garlic,  smashed
• 10 gm ginger, smashed
• 1/2 piece Nam Yue, preserved  bean curd paste, smashed
• 1/4 tsp dark soya sauce
• 3 cups water or more
• 2 tsp Shaoxing wine
• A bit of rock sugar to taste
• Spring onions for garnishing
• Salt to taste
• Oil for frying