On a large rimmed baking sheet, toss squash noodles with 2 Tbsp. oil and ¼ tsp. each of salt and pepper. Heat oven to 400⁰ F and bake noodles for 10 minutes.
In a large pot, heat 1 Tbsp. oil over medium-high heat. Crumble in sausage and brown, stirring, 4 minutes. Remove sausage to a plate using a slotted spoon. Reduce heat to medium.
Add 1 Tbsp. oil to pot, along with onion and mushrooms. Cook 5 minutes, adding ¼ cup chicken stock to scrape up the bits from bottom of pan.
Stir in spinach and cook 3 minutes, until wilted. Stir sausage back into pot and turn off heat.
Remove noodles from oven. In a large non-stick skillet, heat 1 Tbsp. oil over medium-high. Add noodles and cook 6 minutes, tossing with salt and pepper.
Add sausage mixture to skillet and cook 2 minutes.
To serve, divide among 4 bowls and top each serving with 1 Tbsp. Asiago and more pepper to taste.
