To cook in the oven, preheat oven to 400 degrees. Cut the squash in half length-wise and scoop out the seeds with a spoon. Discard the seeds. Drizzle with olive oil and place face down on a baking sheet. Bake for 1 hour or until squash is fork tender.

Once squash is cooked, shred the squash into long spaghetti-like strands by using a fork to scrape the squash widthwise. 

Place the strands of squash in a large mixing bowl.

Add the heavy cream, cream cheese, and butter to a medium sauce pan and cook over medium heat until the butter and cream cheese have melted, stirring often.

Whisk in the ground mustard and pepper.

Remove from the heat and whisk in the cheddar and mozzarella until the mixture is smooth and creamy.

Reduce oven heat to 350 degrees. Spray a 9x13 baking dish with non-stick spray. 

Add the chicken, Ro*Tel, garlic, and onion powder to the mixing bowl with the spaghetti squash.

Pour the cheese sauce over the top and stir gently to coat. 

Pour mixture into the prepared baking dish and bake for 20 minutes or until hot and bubbly. 

Sprinkle with chives before serving.