Spiralize each zucchini into spaghetti noodle shapes using a spiralizer tool.

Salt the zucchini noodles and layout over folded paper towels to remove excess moisture.

Let the zucchini noodles sit for 30 minutes, then squeeze to remove additional water from the vegetable.Preheat oven to 400 degrees Fahrenheit.Melt butter in a large saucepan over medium heat.

Add onion, mushrooms, and garlic to the pan, stirring as needed.

When onions become translucent, add the chopped chicken breast and increase temperature to medium-high.Once the chicken cooks to a white color, add heavy cream to the pan and thoroughly mix while bringing the sauce to a boil.

Reduce heat and allow the sauce to simmer for an additional 1-2 minutes.Remove the sauce from heat and whisk in the xantham gum little by little to thicken.

If you prefer a thinner, runnier sauce, leave this out or cut the amount in half.Arrange zucchini noodles in the bottom of a deep casserole dish.

The zucchini should entirely cover the bottom of the bakeware about an inch thick.

Add the creamy chicken mushroom sauce to the top of the zucchini noodles.

Smooth the mixture evenly over the top to distribute throughout the casserole dish.Sprinkle mozzarella cheese on top and bake for 40 minutes.