3 tablespoons olive oil
1 1/2 pounds skinless boneless chicken breast, cut into strips, and patted dry
1 1/2 cups sliced onions
1 1/2 cups coarsely chopped (about 1-inch pieces) green bell pepper
1 1/2 cups thickly sliced carrots
1 1/2 cups thickly sliced celery
3 cloves garlic, peeled and left whole
Salt and freshly ground pepper to taste
2 teaspoons ground cumin
1/2 teaspoon ground coriander
3 bay leaves
2 cups cubed (about 1-inch pieces) firm, ripe plum or other tomatoes
2 cups cauliflower florets
6 cups water
1 chicken bouillon cube
1 lemon, cut into slices, or to taste
2 cups couscous
1/8 to 1/4 teaspoon Harissa paste
In a casserole set over moderately high heat, warm 1 tablespoon of the oil until hot.
Add the chicken and cook, stirring, until no longer pink.
With a slotted spoon transfer to a plate.
Add the remaining oil to the casserole, the onions, pepper, carrots, celery, garlic, salt, pepper, cumin, coriander, and bay leaves, and cook the mixture over moderate heat, covered, stirring occasionally, for 5 minutes.
Add the tomatoes and cauliflower and cook, stirring, 3 minutes more.
Add the water, bouillon cube, and lemon slices, bring to a boil, and simmer, covered, 5 minutes, or until vegetables are just tender.
Return the chicken to the casserole, add the couscous, and cook over moderate heat, stirring, for 2 minutes.
Add the Harissa paste and salt to taste, stir to combine and let stand, covered, off the heat 5 minutes.
Remove and discard bay leaves before serving.