Cook pasta according to package directions and set aside.

Cook ground meat and minced onion in a skillet over medium heat until the meat is browned and the onion is softened. Drain any excess fat.

In a large bowl, stir together the cooked meat mixture, cream of celery soup, shredded cheddar cheese, lowfat sour cream, lowfat milk, Worcestershire sauce, and thyme (or marjoram or savory).

Add the frozen mixed vegetables and cooked pasta to the bowl and stir to combine thoroughly.

Pour the mixture into a 2-quart casserole dish.

Sprinkle the crushed crackers evenly over the top of the casserole.

Bake in a preheated oven at 375 degrees Fahrenheit (190 degrees Celsius) for 30 minutes, covered.

Remove the cover and bake for an additional 5-10 minutes, or until the topping is golden brown and the casserole is heated through.