Firstly wash the boneless chicken pieces. Rub some salt and tomato sauce if using.
Add all the ingredients for marination except oil and schezwan sauce. Combine all nicely keep them covered or in a ziplock bag. Allow to rest fro 10-15 mins. Now remove the excess water and use them as a stock later for your dish.
Now add the schezwan sauce mix all nicely. Allow to rest for 2-3 mins. The marinated chicken shouldn't have too much moisture.
Spread some corn flour and rice flour on a wide dish /plate. Place oil in a deep pan on high heat. Toss the marinated chicken pieces on the flour, coat from all sides.
Deep fry or shallow fry until evenly cooked and browned from all sides. Place the fried chicken on absorbent napkins to absorb excess oil.
Take another heavy bottomed wok / vessel add oil. Fry the cashews or peanuts and remove them.
In the same oil add garlic and ginger. Saute until the raw smell diminishes.
Time to add all the finely chopped veggies except the greens of spring onion. Toss and saute them on high heat. It's important to fry them on high heat as this would help the veggies in becoming crunchy and cook evenly. If you aren't able to handle the heat then reduce the heat.
Now add the schezwan sauce, fried chicken, roasted cashews or peanuts, vinegar, tomato sauce if using, chili-garlic sauce if using, water and sugar. Simmer for 2-3 mins
Lastly add sichuan pepper, black pepper, greens of spring onion, corn flour dissolved in water or chicken stock, soy sauce and salt. Simmer until gravy thickens or add water if thin consistency required.
Serve the schezwan chicken hot with triple schezwan chicken, fried rice, noodles or soup.