Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 1 1/2 quart casserole dish.
Cook noodles in a large pot of boiling water for 5 minutes, or until almost tender. Drain, and rinse under cold water.
Heat the olive oil in a heavy skillet over medium heat. Cook onion for 4 to 5 minutes, stirring frequently. Add chicken, red bell pepper, celery, and chicken stock. Bring to a boil, and simmer for 5 minutes. Stir in sour cream and oregano.
Spread half of the chicken mixture into the prepared dish. Arrange the asparagus over the chicken, spread cooked noodles evenly over the asparagus, and top with 5 tablespoons of Parmesan cheese. Cover with the remaining chicken mixture. Sprinkle with the reserved Parmesan cheese.
Bake 30 minutes in the preheated oven, until lightly brown.