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
, 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.