This is a sort of authentic recipe, as a tagine should be cooked in a tagine and I cook this in a large saucepan.
Chop and fry the onion in a little vegetable oil and add minced garlic. Then turn down to a low heat and add the spices, keep stirring and let them sweat a little. The saffron is particularly important here, other spices you could use as well are nutmeg, cinnamon, ginger, allspice.
Chop the vegetables into large chunks, up to 2 inches long and 1/2 inch wide. Add the chick peas to the pan once the onions are very soft, then the tomato puree and then the vegetables. Pour in the stock and stir everything in.
Leave on a low heat, stirring occasionally, for about 40 minutes, more time is always good, to get the flavours really infused.
When almost ready, prepare the cous-cous by pouring boiling water and olive oil in a saucepan. Use as much water as stated on packet, leave for 10 minutes then reheat slightly.
You may want a thicker sauce; if so, mix a tablespoon or so of corn flour with a few spoonfuls of the tagine to make a paste then stir back in.
This freezes well, and if thickened, makes a great filling for a wrap/tortilla.