Heat olive oil and 1/2 the butter in a large pot and add the chopped onion, chopped celery, and a seasoning of salt and pepper. Cook, stirring frequently with wooden spoon, till vegetables begin to soften, 4-6 min. Add the chopped asparagus and the thyme, and nutmeg, and stir over high heat until asparagus is tender but stillvibrant green, 3-4 min. Pour in just enough stock (chicken or vegetable) to cover and simmer for 2 min. Remove from heat.