Prepare Your Base: Preheat your oven to 350°F (175°C) and lightly grease a 9x13 inch baking dish.If using frozen spinach, thaw it completely and squeeze out all excess moisture using a clean kitchen towel or cheesecloth. For fresh broccoli, blanch the florets in boiling water for 2-3 minutes until bright green but still firm, then immediately transfer to ice water to stop cooking. Drain thoroughly and pat dry. Create the Protein Layer: Spread the cooked, diced or shredded chicken evenly across the bottom of your prepared baking dish.
Add Vegetables and Aromatics: Distribute your thoroughly drained spinach or blanched broccoli florets over the chicken layer. Sprinkle the minced garlic evenly across the vegetables.
Incorporate Bacon: Scatter the chopped bacon pieces throughout the casserole, ensuring even distribution for consistent flavor in every bite.
Prepare the Creamy Mixture: In a medium bowl, combine the ranch dressing with half of both cheeses (1/2 cup mozzarella and 1/2 cup cheddar). If using optional ranch seasoning, mix it in now for enhanced flavor.
Combine Components: Pour the creamy cheese mixture evenly over the casserole, using a spatula to ensure it reaches all areas.
Begin Baking: Place the casserole in your preheated oven and bake for 15 minutes to allow flavors to meld.
Add the Cheese Topping: After the initial baking period, remove the casserole and sprinkle the remaining cheese (1/2 cup mozzarella and 1/2 cup cheddar) evenly over the top.
Complete Baking and Serve: Return the casserole to the oven for an additional 10-15 minutes, until the cheese is completely melted, bubbly, and beginning to turn golden at the edges.
Allow the casserole to rest for 5-10 minutes before serving to help it set properly.