Boil and mash. Cover the peeled potato chunks with cold water, bring to a boil and simmer for 15 to 20 minutes, until tender. Drain thoroughly, let the steam escape, then mash smoothly by hand. Spread out and cool for about 10 minutes; do not add milk or butter.
Mix the dough. Stir in the cornstarch, vegan mayo, parsley, green onions, paprika, garlic powder, salt, optional chili flakes and black pepper. The cooled dough should hold together and roll without sticking. If needed, add extra cornstarch 1 tablespoon at a time, stopping as soon as it is shapeable.
Shape. On a lightly dusted surface, roll small portions into ropes about 5 inches (13 cm) long and 1/2 inch (1 cm) thick. Join the ends and press the seam firmly closed. Keep the thickness even; the number of rings will depend on their size.
Chill if needed and make the dip. If the rings feel soft when lifted, refrigerate for 15 to 20 minutes. Stir the dip ingredients together, adding the chipotle gradually to taste. Keep refrigerated until serving.
Heat the oil and test one ring. Heat about 2 inches (5 cm) of neutral oil in a deep, heavy pot to 340°F (170°C), filling the pot no more than halfway. Lower in one ring and leave it undisturbed for about 2 minutes before turning. If it breaks, check the dough and seams before frying the rest.
Fry in batches. Fry a few rings at a time for about 4 to 5 minutes, until golden and crisp, turning gently once the crust has set. Keep the oil near 340°F (170°C) and allow it to recover between batches.
Drain and serve. Lift the rings onto a rack set over a tray. Serve hot with the chipotle mayo on the side and extra chopped herbs if desired.
Notes
Dough: Start with the listed cornstarch and add more only if the cooled dough is sticky. Too much makes the rings dense.Yield and timing: Makes about 4 snack servings; the number of rings depends on their size. Allow an extra 15–20 minutes if chilling is needed.Make ahead: Refrigerate shaped rings, covered, for up to 1 day before frying. They are crispiest freshly fried; refrigerate cooked leftovers in a covered container for up to 3 days.