Cook the large spaghetti squash first. You can steam this in the Instant Pot Pressure Cooker or you can bake it in the oven.
Cook the Sausage:
While the spaghetti squash is cooking, start frying the breakfast sausage in a frying pan over medium heat until it’s browned.
Set aside.
Make the Noodles:
Once the spaghetti squash has been baked, you will need to make the spaghetti squash noodles.
Remove the seeds from the spaghetti squash if this was not done during the baking method.
Use a fork to scoop out the spaghetti squash noodles by piercing the squash and dragging the fork along the top of the squash. The noodles will come out in long strips. Repeat this step until you get all the noodles out of each side of the squash halves.
One large spaghetti squash may yield between 4 to 5 cups of spaghetti squash noodles.
Depending on the size of your spaghetti squash you may need to use a square baking dish or a rectangle baking dish for larger spaghetti squashes.
Spray the baking dish with nonstick cooking spray. Set aside.
Make the Creamy White Sauce:
In a saucepan over low heat, melt the butter and add the heavy cream, unsweetened almond milk, garlic, salt, white pepper, Dijon mustard, cream cheese, parsley, and Parmesan cheese.
Mix the white sauce until all in combined and it’s smooth and creamy.
Add the mushrooms last.
Assemble the casserole:
In the prepared baking dish, spread out the spaghetti squash noodles evenly. Sprinkle the sausage over the spaghetti squash evenly.
Pour the white sauce over the spaghetti noodles.
Sprinkle the mozzarella cheese over the top of the spaghetti squash casserole and bake it at 350 degrees for 20 to 25 minutes or until the casserole is completely warm inside and the cheese on top has melted.
Turn the oven to broil for the last 4 to 5 minutes to melt the cheese fully to a golden brown color.