Place the tomatoes and chilli on a baking tray. Sprinkle with a little olive oil and season to taste with salt, pepper and sugar. Roast in the oven at 190ºC for 30 minutes or until the tomatoes are lightly browned.
Meanwhile, heat some olive oil in a saucepan and add the coriander seeds, cloves, aniseeds, onion, celery, garlic and ginger. Sauté over medium-low heat for 20 minutes or until the onion has softened and caramelized, stirring occasionally.
Add the tomatoes and their pan juices to the sautéed vegetables. Add the vinegar, brown sugar and chopped basil stalks. Bring to a boil, reduce heat and simmer for 10 minutes without a lid, stirring occasionally. Taste and adjust seasoning if necessary with more salt, pepper, chilli, vinegar and sugar. Stir in the basil leaves and puree the mixture in a processor or with a stick blender.
Return the mixture to the saucepan and continue to cook without a lid until it has reduced and thickened to your liking. Now strain the mixture and allow to cool down completely before storing in the fridge.
Yields about 750 ml ketchup