Turn the slow cooker on to high or low.
Put the peppers, onions, garlic, tomatoes, potatoes, capers, vinegar and caster sugar in the slow cooker dish and season with salt and freshly ground black pepper. Mix well to combine. Cover with the lid and cook for 4 hours on high or 8 hours on low setting until the peppers are meltingly soft and juicy.
Stir in the basil and serve hot, warm or cold. Spoon into bowls, scatter over the feta cheese and pinenuts and eat with crusty bread to mop up the juices.
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