1. In a large pot, heat some oil over medium heat. Add diced chicken and cook until browned.

2. Add chicken broth and bring to a simmer. Stir in great northern beans, corn, and spinach.

3. In a bowl, mix together mayonnaise and dijon mustard. Gradually whisk in some of the hot broth from the pot to temper the mixture.

4. Pour the mayonnaise mixture into the pot and stir well. Let the soup simmer for another 10-15 minutes, stirring occasionally.

5. Season with salt and pepper to taste before serving.