Meanwhile, in a medium saucepan, heat the oil. Add the shrimp shells; cook over moderately high heat, stirring often, until beginning to brown, about 3 minutes. Add the chopped fennel, onion, celery, carrot, garlic, fennel seeds and Aleppo pepper and cook over moderately high heat, stirring often, until the onion is golden, about 6 minutes. Add the wine and boil until almost evaporated. Add 2 cups of the chicken stock and simmer over moderate heat for 12 minutes. Strain.