Season chicken on both sides with garlic salt. Preheat skillet to a medium/high and cook chicken until golden brown. Poke with a knife to see if the chicken is cooked through. Let the chicken rest for about 5 minutes and dice it into one inch cubes.
Dice, chop and prepare ingredients for cooking the soup.
Melt the butter with oil in a large saucepan over medium heat. Add onion, celery, carrots and garlic. Cook, stirring occasionally, until the veggies softens. Whisk in the flour and cook for about 1 minute.
Add in the half-and-half, cooked chicken, bring to a simmer. Add in chicken broth and bring it to a simmer again.
Add gnocchi and simmer until gnocchi are fully cooked. Add spinach and remove from the heat.
Serve while the soup is warm, it also reheats well.
Stir soup occasionally to prevent it form sticking to the bottom of the cooking pan.