Blend garlic, cilantro leaves and black peppercorns in a food processor, with a little water, to form a thick paste.
Heat oil. Fry paste lightly until it begins to brown.
Add coconut milk and stir in.
Stir in all remaining ingredients.
Add a little water as needed to give it a sauce consistency. Cover, reduce heat to low and let it cook, stirring occasionally till the potatoes are fully cooked. Add small dashes of water to prevent drying or burning and to keep the sauce consistency.
Remove from heat. Add a few drops of lemon or lime juice to taste. It should have a slight tang but not be sour.
(Tip: to thicken the sauce a little, mash a few of the chickpeas while cooking, and this makes a good thickener).