Hangzhou Broad Beans with Ham

Name: Hangzhou Broad Beans with Ham (Huo Tui Can Dou 火腿蠶豆)
Cuisine: Chinese
Ingredients: Salt; 50 g Chinese or Spanish cured ham; ¼ tsp caster sugar; 75 ml stock or water; ½ tsp potato flour mixed with 2 tsp cold water (optional); 2 tbsp cooking oil; 300 g podded broad beans (just over 1 kg in the pod)