METHOD

1. To make the stock, place the hock, onion, bay leaves, thyme, garlic and water in a large saucepan over high heat and bring to the boil (ensure there is enough water to cover the hock). 
   
2. Reduce heat to medium and cook for 1 hour–1 hour 15 minutes or until the ham is tender. Remove the hock and set aside to cool slightly. 
   
3. Using 2 forks, shred the meat and set aside, discarding bone and skin. Strain the stock and set aside.
   
4. Heat the oil in a large saucepan over high heat. Add the onion and garlic and cook for 3–4 minutes or until softened. Add the celeriac and 1.5 litres of the reserved stock+ and bring to the boil. Cook for 12–15 minutes or until the celeriac is tender. 
5. Add the peas and cook for 1 minute or until soft. Remove from the heat and add the watercress and yoghurt. Using a hand-held stick blender, blend until smooth. 
   
6. Divide the soup between bowls and top with the reserved shredded ham and mint leaves. Sprinkle with chia seeds to serve. Serves 4–6.

+ Any remaining stock can be kept frozen in an airtight container for up to six months.