Fill a large pan with water.

Add the pork to the water and bring to a boil.

Simmer for 5 minutes, then remove the pork and discard the water.

While the meat simmers, trim the green onions, discarding the darkest green parts, and chop them.

Peel the ginger and cut into matchsticks.

Peel and finely slice the garlic.

Return the pan to the heat and add the peanut oil.

Warm the oil over medium heat, then add the green onions, ginger, and garlic and soften, stirring to prevent browning.

Place the pork into the pan.

Add the sugar, soy sauce, rice wine, salt, star anise, five-spice powder, crushed chiles, and cinnamon stick.

Pour in the stock.

Bring to a boil, then reduce heat to a simmer and cover.

Cook gently for 1 hour, checking the liquid level occasionally.

Turn the pork over, ensuring the other half is submerged in the broth, cover, and cook for another hour.

Peel and chop the celery root.

Boil the celery root in salted water until tender (about 20-25 minutes).

Drain the celery root thoroughly.

Put the drained celery root in a food processor.

Add the butter and black pepper to the food processor.

Process until smooth puree is achieved.

To serve, place a large spoonful of celery root puree in a shallow bowl.

Carve the pork into coarse slices (it will naturally fall apart).

Arrange the pork slices alongside the puree.

Pour a ladleful or two of broth around the edge of the bowl.

Serve with spoons for the broth.