Put big bone in a deep pot with enough water. Turn to high heat.
When water boils, take the big bone out and rinse. Pour the water in the pot out.
Big bone in the pot again with enough water. Turn to medium heat. When water boils, turn to low heat. And slow cook for at least half an hour. I cooked it for 1 hour.
Add in white gourd pieces and some wolf berries. Simmer for at least another half an hour.
Sprinkle salt to season and some chopped spring onion. And ready to serve.