This recipe is all about technique, especially when it comes to the zucchini. Following these steps carefully will ensure your bake is creamy and delicious, not watery. We’ll break it down into four main stages: preparing the zoodles, cooking the chicken and sauce, assembling the casserole, and baking to perfection.

Step 1: Preparing the Zoodles (The Most Important Step!)

The key to avoiding a soggy casserole is to remove as much moisture as possible from the zucchini before baking. This process is called “sweating” and is non-negotiable for a great result.

1. Spiralize the Zucchini: Using a spiralizer, turn your four medium zucchini into noodles. If you don’t have a spiralizer, you can use a julienne peeler or simply slice the zucchini into very thin “planks” and then cut those into noodle-like strips.
2. Salt and Sweat: Place the zoodles in a large colander set over a bowl or in the sink. Sprinkle them generously with about 1 teaspoon of salt and toss gently to distribute it. Let the zoodles sit for 20-30 minutes. You will be amazed at how much water collects in the bowl beneath. The salt draws out the excess moisture through osmosis.
3. Squeeze and Dry: After sweating, take handfuls of the zoodles and squeeze them firmly over the sink to remove even more water. Be gentle but firm. Once squeezed, lay them out on a clean kitchen towel or several layers of paper towels. Roll them up in the towel and press down to absorb any remaining moisture. Set the dried zoodles aside. This double-drying method is the secret weapon against a watery bake.

Step 2: Cooking the Chicken and Aromatics

While the zoodles are sweating, you can prepare the flavorful chicken and sauce base.

1. Preheat Oven and Prepare Dish: Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish or a similar 3-quart casserole dish.
2. Sauté Chicken: Heat the olive oil in a large skillet or Dutch oven over medium-high heat. Add the cubed chicken breast and season with a pinch of salt and pepper. Cook for 5-7 minutes, stirring occasionally, until the chicken is lightly browned on all sides and cooked through. Use a slotted spoon to remove the chicken from the skillet and set it aside on a plate.
3. Cook Aromatics: In the same skillet, add the chopped yellow onion. Sauté for 3-4 minutes until it becomes soft and translucent. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.

Step 3: Creating the Creamy Sauce

Now it’s time to transform the skillet into a vessel of creamy, savory goodness.

1. Build the Sauce: To the skillet with the onions and garlic, add the drained diced tomatoes, softened cream cheese, grated Parmesan cheese, Italian seasoning, 1/2 teaspoon of salt, and 1/4 teaspoon of black pepper.
2. Melt and Combine: Stir constantly over medium heat until the cream cheese is fully melted and all the ingredients have combined into a smooth, creamy sauce. This should take about 3-4 minutes.
3. Taste and Adjust: Give the sauce a taste and adjust the seasonings if necessary. It should be rich, savory, and well-balanced.

Step 4: Assembling and Baking the Casserole

This is where all the components come together to create the final masterpiece.

1. Combine Ingredients: Turn off the heat. Add the cooked chicken and the thoroughly dried zoodles back into the skillet with the sauce. Add 1 cup of the shredded mozzarella cheese.
2. Mix Gently: Using tongs or two large spoons, gently toss everything together until the zoodles and chicken are evenly coated in the creamy sauce. Be gentle to avoid breaking up the zoodles too much.
3. Transfer to Baking Dish: Pour the entire mixture into your prepared 9×13-inch baking dish and spread it into an even layer.
4. Top with Cheese: Sprinkle the remaining 1/2 cup of shredded mozzarella cheese evenly over the top of the casserole.
5. Bake to Perfection: Place the dish in the preheated oven and bake for 20-25 minutes. The casserole is done when the sauce is bubbly and the cheese on top is melted and has started to turn a beautiful golden brown.
6. Rest and Garnish: Remove the casserole from the oven and let it rest for at least 5-10 minutes. This allows the sauce to set up slightly and makes it easier to serve. Garnish with fresh chopped basil or parsley before serving, if desired.