Chop the chicken breast into bite-sized chunks. Peel and finely dice the onion and garlic, and grate the ginger.
Heat 1 tablespoon of vegetable oil in a medium pot on high heat. Transfer the chicken chunks to the saucepan and roast them for 2-3 minutes until slightly browned. Remove them from the pot and set them aside.
Add the other tablespoon of vegetable oil to the same pot. Turn down the heat to medium and add the onion. Roast for about a minute until translucent.
Now, add the ginger, garlic, tomato paste, curry powder, coriander, salt, and red pepper flakes (optional). Roast for a couple of seconds, stirring frequently.
When the spices are fragrant, pour the coconut milk and chicken stock into the pot and add the cinnamon stick. Add the roasted chicken. Let the curry cook on low to medium heat for 15 to 20 minutes.
Remove the cinnamon stick when the curry is cooked. Top with chopped cilantro or parsley and serve with whole-wheat rice or naan.