Season chicken with garlic, salt, pepper and nutmeg. Leave to marinate for 1/2 hour.
In a large pot, heat oil. Add onion and cook until onions soften.
Add chicken and stir fry for 5 minutes, stirring occasionally.
Add tomatoes, 1 cup water, chile, chayote, sugar, thyme, cayenne, oregano and garam masala. Bring to a boil. Reduce to a simmer and cook for 15 minutes.
Add parsley and adjust salt as needed. Cook for 1 more minute.