Step 1

Preheat the oven to 375ºF.

Step 2

Cut the squash in half lengthwise; remove and discard seeds. Place squash on a baking sheet cut side down. Bake until tender, about 1 hour.

Step 3

Separate the strands of squash with a fork and place in a medium bowl; discard shells. Squeeze out any excess liquid from the squash if watery.

Step 4

Maintain the oven temperature.

Step 5

Heat butter and oil in a large saucepan over medium heat. Add onions and cook about 2 minutes.

Step 6

Stir in flour. Reduce heat to low and cook, stirring continually 3 - 4 minutes.

Step 7

Add milk and chicken broth and continue whisking, raising heat to medium-high until it comes to a boil and becomes smooth and thick, about 2 minutes stirring; season with salt and pepper.

Step 8

Once it becomes thick, remove from heat, add cheddar cheese and mix well until cheese is melted.

Step 9

Adjust salt and pepper to taste, add cooked spaghetti squash and baby spinach, pour into a baking dish and sprinkle parmesan cheese on top.

Step 10

Bake until bubbly and golden 25 to 30 minutes.