Preheat oven to 375 degrees. Cook spaghetti squash first. To do this, simply cut it in half, scoop out and discard seeds. Next place face down in a shallow pan with a bit of water, then bake for 30-40 minutes or until tender. Pull it out of the oven and let cool, then scrape out the flesh with a fork.
Increase oven to 400 degrees. Line pizza pan with parchment paper.
In a [large bowl|http://www.shareasale.com/m-pr.cfm?merchantID=40174&userID=419949&productID=514151555], combine spaghetti squash, mozzarella cheese, egg, egg whites, garlic, spices, salt and pepper. Mix together until well combined. Set aside for about 5 minutes. Drain any liquid forming at the bottom of the bowl. Press squash mixture evenly into parchment paper lined pan.
Bake for 12-15 minutes. While the crust is baking, saute the mushrooms and onion until mushrooms are soft and onions are translucent. Remove from heat. Remove pizza crust from oven when crust appears dry and golden.
Spread [Garden Good sauce|http://www.shareasale.com/m-pr.cfm?merchantID=40174&userID=419949&productID=498891642] over the crust. Sprinkle your onion, mushrooms and arugula over sauce. Top with cheeses. Return to 400-degree oven and bake another 10-15 minutes until cheese is bubbly and edges of crust are browned. Cool for about 5 minutes before cutting into the pizza. Tip: It may be easier to lift the parchment paper off of the pizza pan and place on [cutting board|http://www.shareasale.com/m-pr.cfm?merchantID=40174&userID=419949&productID=512761330].