
Blanch the lotus rootIn a pot, bring 3 cups (750 ml) water and the apple cider vinegar to a boil. Add the lotus root and blanch for 2 to 3 minutes if using frozen slices, or 4 to 6 minutes if using fresh. Drain well and set aside.
Prepare the sauceIf using kelp stock: Soak a small piece of dried kelp (kombu) in 1/2 cup (125 ml) water for 10 minutes, then remove the kelp. Add the soy sauce, mirin, garlic, and brown sugar directly to the kelp water, stirring until the sugar is fully dissolved. If using plain water, combine these ingredients with 1/3 cup (80 ml) water instead.
Simmer with sauceIn a wide non-stick pan or braiser, heat the cooking oil and add the blanched lotus root. Stir briefly over medium heat. Add the prepared sauce and stir until the slices are evenly coated. Continue cooking until the liquid reduces to about one-third of its original volume and begins to thicken.Add the golden syrup (or rice syrup, or corn syrup) and stir continuously over medium to medium-low heat until the sauce turns glossy and coats the lotus root. If it begins to dry out too much, reduce the heat to prevent burning.
Finish and serveWhen the sauce is mostly reduced, add the sesame oil and sesame seeds. Give it a quick stir to combine. Serve at room temperature or chilled.