Preheat oven to 400.

Once the seeds and membranes are removed from the two halves of the spaghetti squash, drizzle on the olive oil, salt, and pepper. Rub all over so the oil covers the inside of the spaghetti squash. Place cut-side-down in a large 13×9 Pyrex dish (or other baking dish). Bake at 400 for 50-60 minutes, until the skin is tender to the touch.

Remove from oven and allow to cool. Reduce oven to 350.

Meanwhile, make your Bolognese sauce. In a large skillet, brown the ground sirloin over medium-high heat (about 8 minutes).*

Shred the spaghetti squash and place into a large sieve or colander to drain while the Bolognese sauce simmers. Occasionally move the spaghetti squash around and gently push on it with tongs to remove the excess water. Save the spaghetti squash shells for baking later on.*

Once the beef has browned, add in your marinara sauce, stir to combine, and lower to a simmer. Cook until the sauce has thickened slightly (about 5 minutes). Remove from heat.

Place the drained, shredded spaghetti squash in a large bowl. Carefully pour the Bolognese sauce over top. Add in ¼ cup mozzarella and toss to combine with tongs. Divide the mixture evenly between the two spaghetti squash shells. Top with remaining ¼ cup mozzarella cheese and Parmesan cheese and bake at 350 until cheese has melted and the mixture is heated through (about 15 minutes). Broil the tops of the spaghetti squash for 2 more minutes to get the cheese brown and bubbly.

Garnish with julienned basil.