In a large, heavy-bottomed pot, melt the butter (or oil) over medium-low heat. Add the lamb, onion, garlic, salt, cinnamon, coriander, cumin, vanilla bean powder, red pepper flakes (if using), apricot preserves and vinegar and cook, stirring frequently, until the aroma of the spices is strong, about 5 to 7 minutes. (Do not allow the meat to brown.)
Add chickpeas and stock, bring just to a simmer, then reduce the heat to low, cover and simmer gently until the lamb is very tender, about 1 hour 15 minutes. Add the raisins or apricots and continue to cook, uncovered, until they are nicely plumped, about 10 minutes more. Remove from heat, adjust salt and add pepper, then stir in the parsley, mint and lemon juice, top with toasted almonds if using and serve over couscous.