While most people refer to all four of the pig's limbs as the feet (or trotters), Chinese butchers call the front legs (which are larger, meatier and more expensive) the "hands" and the back legs (which are bonier and harder to eat) the "feet". Which of the two you use is up to you, but for both types, ask the butcher to cut them in half lengthwise, then into pieces about 4cm (1 ½in) wide. You should also have the butcher singe off any hairs left on the feet.
If you can find it, use glutinous rice wine (mijiu) for this dish; it has a milder flavour than the Shaoxing rice wine commonly used.
Rinse the pig's feet under cold running water. Bring a large pot of water to the boil, add the pieces and simmer for about five minutes. Unless your pot is very large, you'll probably have to do this in batches. Drain the feet and rinse them well. Bring a fresh pot of water to the boil and repeat this process (this rids the feet of impurities).
Wash the pot. Rinse the ginger (no need to peel it) and cut it into large chunks. Put the pieces on a cutting board and lightly crush them with the side of a cleaver. Put the ginger into the pot, then add the garlic. Break the dried chillies in half, shake out and discard the seeds, then put the chillies into the pot. Add the soy sauce, rice wine, cinnamon sticks, star anise, sugar, chun pei and 1 tsp of salt into the pot, along with 600ml (2¼ cups) of water. Bring to a simmer and cook until the sugar is dissolved.
Put all the pieces of pig's feet into the pot and bring to the boil. Cover with the lid, turn down the heat and cook at a low simmer, occasionally moving around the pieces of pig's feet so they are submerged in the liquid. After about an hour, add the peanuts.
Simmer the ingredients for about three hours in total, or until the pig's feet pieces are very tender. The sauce should reduce to a sticky, light syrupy consistency; if it's too thin, remove the lid when the meat is tender and continue to simmer. Taste the sauce and correct the seasonings, if necessary.
Remove the pieces of pig's feet and put them in a large serving bowl. Add the fu pei to the pot, if using, and simmer it in the sauce until soft. Ladle the sauce and fu pei over the pig's feet. Cut the spring onions into 1cm pieces and scatter them and/or fresh coriander sprigs over the ingredients before serving.