Combine all vegetables in the bottom of a 5-quart slow cooker.
Season chicken fillets with salt, pepper, and 1 tablespoon of leek soup mix. Place chicken in slow cooker on top of vegetables.
In a medium bowl, whisk together asparagus soup, white wine, and remaining leek soup mix. Pour over chicken.
Cover and cook on LOW setting for 4 hours.
Strain and de-fat or de-grease the cooking liquid. Serve as sauce on the side.