Garlic, Garbanzo and Spinach Soup (T&T)

We had this for supper earlier in the week - I thought it was outstanding. I have modified the recipe somewhat to reduce the fat. (The original recipe used twice the amount of olive oil and heavy cream instead of the fat-free half-and-half or soymilk). I served it with toasted whole wheat bread.

Source: Adapted from The Best-Ever Vegetarian Cookbook by Nicola Graimes, 1999

Yield: 2 1/2 quarts

2 tablespoons olive oil
2 onions, coarsely chopped
8 cloves garlic, crushed (or 4 teaspoons minced garlic)
4 teaspoons ground cumin
4 teaspoons coriander
8 cups water
3 vegetable bouillon cubes
4 large potatoes, peeled and cubed
1 (30 ounce) can garbanzo beans, drained
2 tablespoons cornstarch
1 1/2 cups fat free half-and-half (or soymilk)
1/4 cup tahini
1 (10 ounce) package frozen spinach (leaves or chopped)
Salt, to taste
Cayenne pepper, to taste

Heat the oil in a large saucepan over medium-high heat. Saut