Cut the thighs into bite-sized pieces, roughly 3cm x 3cm (1" x 1").
Marinate them in the five spice powder, chicken bouillon powder, salt, sugar, grated ginger, finely chopped garlic, onion powder, corn starch, egg white, Shaoxing wine, light soy sauce, pepper and mashed fermented tofu for at least 20 minutes.
Toast the white and Sichuan peppercorns on low-medium heat until slightly brown.
Use a spice grinder to grind the peppercorns into a powder. Alternatively, use a mortar and pestle.
Combine the ground peppercorns with the five spice powder, paprika and salt.
Mix the potato starch and baking powder together, then coat the cut pieces in the batter. Use a colander to shake away any excess starch.
Heat up a wok of oil on medium heat and fry the coated pieces for 5 minutes or until golden.
Remove the pieces and let it drip dry in a sieve. Turn the heat up to high and double fry them for another 2 minutes.
Just before the chicken is ready, toss in the Thai basil leaves and let them fry for 2 minutes or until crispy. Scoop the chicken and leaves out into a large sieve or colander.
Put a serving of Taiwanese Popcorn Chicken into a platter along with some Thai basil. Add some of the spice mix in and toss all together until the pieces are evenly coated.