Brown chicken pieces well in oil one after the other, then place in Pyrex dish.
Mix melted butter with lemon juice, water, salt and Vegeta and pour over chicken pieces.
Peel and dice celery and carrots and slice leek and celery stalk and distribute evenly between chicken pieces. Cover and bake in oven preheated at 200°C for about one hour.
In the meantime prepared the sauce. Briefly brown flour in melted butter. Add 200 ml of coconut milk, salt and pepper and simmer gently until thick, constantly stirring.
Mix sugar, mustard and vinegar into the remaining coconut milk and stir until slightly thick.
Mix together both mixtures to obtain compact sauce.
Remove roasted chicken with vegetables from oven, pour over with sauce and serve with cooked rice.
Sauce can also be served separately.