In a Dutch oven, brown chicken in 2 tablespoons butter. Remove and keep warm. In the same pan, saute the onion, carrot, celery and garlic in remaining butter until tender., Whisk in flour until blended; gradually stir in the milk, cream, bouillon and pepper. Bring to a boil. Reduce heat; cook and stir until thickened, about 2 minutes., Add the gnocchi and spinach; cook until spinach is wilted, 3-4 minutes. Add the chicken. Cover and simmer until heated through (do not boil), about 10 minutes.