Preparation

• Gather all ingredients. Preheat the oven to 350 degrees F (175 degrees C).
• Place garlic cloves in a small oven-safe dish, and roast in the preheated oven until softened and fragrant, about 20 minutes. Set roasted garlic cloves aside to cool.
• Place spinach in a large mixing bowl; stir in the artichoke hearts.
• Melt butter in a skillet over medium heat. Add mushrooms; cook and stir until mushrooms are softened, about 10 minutes. Mix in green onions, and cook and stir until onions are soft, about 5 more minutes.
• Transfer mushroom mixture into the bowl with spinach mixture.
• Remove cream cheese from wrapping, place into a microwave-safe bowl, and cook in the microwave until warm and very soft, about 1 ½ minutes. Stir softened cream cheese into spinach mixture, and add sour cream, water chestnuts, Parmesan cheese, mayonnaise, garlic salt, and lemon juice.
• Squeeze roasted garlic out of garlic skins, and mix thoroughly into the spinach mixture. Spoon the casserole into a round 2-quart baking dish.
• Bake in the preheated oven until the casserole is hot and bubbly, about 30 minutes.
• Spread French-fried onion rings over the top, return to the oven, and bake until the onion rings are lightly browned, 5 to 10 more minutes.