Preheat the oven to 400 degrees F. Using a small sharp knife, pierce the skin of the duck all over, but be careful not to tear holes in the skin. Sprinkle the duck with salt and the ground Sichuan pepper, place on a wire rack set in a roasting pan and roast for 25 minutes.
Pour any excess fat into a jug. Reduce the oven temperature to 250 degrees F. When at 250 degrees F, return the duck to the oven, and cook for a further 1 1/4 hours, basting with the reserved fat every 20 minutes.
While the duck is roasting, bring the stock up to the boil in a large pot with the thyme, butter and lemon rind. Add the lettuce to the stock, and cover with a lid or tinfoil. Turn the heat down, and braise for 8 to 10 minutes, or until the lettuce starts to wilt. Remove from the heat, and keep warm until ready to serve.
Remove 90 percent of the duck fat from the roasting pan, and pour the honey over the duck. Turn the oven up to 350 degrees F, and put the duck back into the oven for a further 15 to 20 minutes, basting every 5 minutes and making sure the honey doesn¿t burn. On the final baste, drizzle the soy sauce over the duck. When cooked, remove the duck from the oven and set aside to rest.
While the duck is resting, make the potato pancakes. Mix the cold potatoes, flour and baking powder together. In a separate bowl or jug, whisk the eggs and milk together; pour into the potato mixture, and gently stir to make a batter (don't worry about a few lumps). Stir in some salt and pepper. Fry spoonfuls of the batter mix in a nonstick frying pan with a little oil until golden brown on each side. Remove the pancakes from the heat, and keep warm.
Carve the duck, and serve with the braised lettuce and the potato pancakes. Spoon a little of the cooking liquor from the lettuce over the top, and tuck in.