Heat a pan or wok on high heat with olive oil, fry the chicken pieces until cooked through (74°C / 165°F internal temperature), then set aside and keep warm.
Clean and chop the leeks, zucchini, half of the pumpkin, and the sweet potato into roughly similar-sized pieces.
In the same pan, heat a mixture of olive oil and butter on medium heat, add the prepared vegetables, and cook for 4 minutes, stirring occasionally.
Stir in the peanut butter until well combined, cooking for 1 minute.
Pour in the Cremefine or cream, bring to a boil for 2 minutes, stirring occasionally.
Reduce heat to low, stir in the yogurt until well incorporated.
Season to taste with salt, pepper, coriander, turmeric, and fig mustard or mango chutney.
Return the cooked chicken to the pan and stir gently.
Simmer on low heat for 10 minutes, being careful not to overcook the sweet potato pieces.
Taste and adjust seasonings; add chilli powder if you prefer a spicier dish.