Preheat oven to 350 degrees.
Spray a 9x13 casserole dish with cooking spray.
Heat a skillet on medium-high heat. When hot, add the olive oil, onions and garlic. Cook for 2-3 minutes until fragrant.
Add the chicken cubes to the skillet and season with the chicken seasoning, salt, and pepper to taste. Cook the chicken for 4-5 minutes, stirring and flipping the chicken until it is no longer pink on each side.
Remove the chicken, onions, and garlic and set aside on a plate.
Add the butter to the skillet on medium-high heat. Allow the butter to melt and then add the xanthan gum. Use a whisk and stir until combined. This will create a roux and the sauce should thicken.
Pour in the chicken broth. Whisk to combine. Then add the cream cheese and heavy whipping cream. Whisk. Lower the heat to medium and allow it to cook for 3-4 minutes until thick.
When thickened, add the cooked, steamed broccoli and stir. Then pour the mixture into the casserole dish with the chicken mixture.
Sprinkle the shredded cheese throughout the top.
Bake for 18-22 minutes until the cheese begins to bubble.
Cool before serving.