Place the dried chickpeas in a bowl, cover with cold water, add a pinch of bicarbonate of soda, and soak overnight.
Drain the chickpeas, rinse well, and place in a large saucepan with the half of an onion or 1 head of garlic. Cover with 2 liters (2 quarts) of cold water and bring to the boil. Reduce the heat to a simmer, skimming off any scum, and cook for 1-2 hours or until soft and tender. Drain the chickpeas, saving about 1 cup of cooking liquor. You do not have to remove the skins on the chickpeas.
Place the chickpeas in a food processor and puree the chickpeas until quite smooth. Add enough cooking liquor or water so they are similar to wet mashed potato. Set aside.
Just before serving the lamb, in a medium saucepan, heat up the olive oil over a medium to high heat and add the onion, garlic and cumin. Fry, stirring until the onion and the garlic are evenly golden brown. When ready, add the chickpea puree and the saffron infusion. Simmer for 5 minutes and sprinkle salt and pepper to taste. Serve warm, sprinkled with the chopped parsley.