Take chicken cubes in a bowl, add oyster sauce and marinate for at least one hour. Heat oil in a pan, add sliced spring onions and sauté. Add garlic and continue to sauté.
Add peanuts and sauté. Add chicken cubes and sauté for two minutes. Add green chillies, half of the crushed black peppercorns, red chilli flakes and stir.
Add cinnamon powder, salt, tomato ketchup and stir. Dissolve cornflour in half a cup of water. Add lemon juice to the pan and stir.
Add a cup of water and dissolved cornflour and cook till it thickens. Add spring onion greens.
Serve hot sprinkled with remaining crushed black peppercorns.