Lisa's Chicken Au Gratin - Walter Stewart's Market

Ingredients

• 3 tablespoons extra-virgin olive oil
• 1 pound mushrooms, cleaned and sliced
• 2 tablespoons fresh thyme leaves, chopped
• 2 garlic cloves, chopped
• 4 boneless, skinless chicken breasts; cut into bite-sized pieces
• salt and freshly ground pepper
• 1 ½ cups frozen pearl onions, thawed
• 2 cups low-sodium chicken stock (check label if you want gluten-free)
• ½ cup evaporated skim milk
• 2 cups baby spinach leaves
• zest of 1 lemon