In a microwave safe bowl or plate, add the onions, carrots and celery.
Cook in microwave for about 4 minutes until soft.
In a large nonstick pan or pot, melt butter.
Add garlic and cooked vegetables.
Season with a little salt and pepper.
Mix well and cook for 1 minute.
Stir in flour and mix well.
Continue to cook for 2 minutes, stirring often.
Stir in chicken broth, 1 cup at a time, mixing after each.
Pour in milk and stir well. Add cooked chicken.
Bring up to a simmer and continue to simmer uncovered for 20 minutes, stirring often.
In the meantime, cook the potato gnocchi separately, according to package directions.
When soup is finished, add cooked gnocchi and spinach.
Simmer for about a minute until spinach is wilted.