Pat the chicken thighs dry with paper towels. Place in a bowl.
Whisk together all the ingredients for the dry rub. Add to the chicken and mix well.
Cover the bowl. Marinate the chicken in the fridge for at least six hours (overnight is best).
Using a food processor or a mortar and pestle, grind the ingredients for the coating excluding the flour and starch. Do NOT grind too finely. Visible specks of the individual spices, especially the Sichuan peppercorns and fennel seeds, add better texture to the coating.
Whisk the flour and starch in a bowl. Add the ground spices. Stir to blend evenly.
Heat the cooking oil in a frying pan to 350F.
Dredge each chicken thigh in the seasoned flour, dip in the beaten eggs, then dredge in the flour a second time. Shake off the excess.
Fry the chicken in the hot oil for eight to 10 minutes until cooked through and the coating is crisp. If your frying pan is rather small, fry the chicken in batches to avoid the temperature of the oil from dropping.
Drain the 3-pepper fried chicken on a stack of kitchen paper to get rid of excess oil. Serve at once.