Rinse the wild rice. Add the chicken breasts, chicken broth, chopped onion, carrots, celery, wild rice, and minced garlic into the crockpot. Then add one teaspoon each of garlic powder, salt, pepper, minced onion, and dried parsley. Mix the ingredients in so they are all covered by the broth.
Cover and cook on high for 4 hours (or until the chicken is fully cooked and the vegetables are soft). Crockpot temperatures vary, so the timing for your soup may take a bit less or more time. The chicken is fully cooked when it reaches an internal temperature of 165 degrees Fahrenheit. You can use a meat thermometer to check if you're unsure.
Once the soup is ready, add the butter, flour, garlic powder, and minced onion to a medium saucepan on the stove at medium heat. Whisk the ingredients together as the butter melts. Once the mixture resembles a thick paste, gradually add the heavy cream, whisking continuously. The mixture should be nice and thick. Pour it into the crockpot and mix the soup to combine the ingredients.
Finally, using a fork or tongs, remove the chicken breasts from the crockpot. Dice the chicken into small pieces or shred the chicken with a fork--whatever you prefer. Add the chicken back into the crockpot and serve hot. Top with fresh parsley.