Carefully cut the spaghetti squash in half lengthwise. Clean out the seeds and discard or save them for another use.
Cut the top off the pumpkin (if making the puking pumpkin version). Clean, seed, and carve a face on the pumpkin.
Brush the flesh of the spaghetti squash with 1 tablespoon of olive oil and sprinkle with 2 teaspoons of salt and 1 teaspoon of pepper.
Place the spaghetti squash, flesh side down, on a baking sheet and place into a pre-heated 425-degree oven (along with the pumpkin, optional) for 30 - 40 minutes. Cool completely.
Once the spaghetti squash is cool enough to handle, use a fork to scrape the strands of the spaghetti squash out of the shell.
In a large skillet, melt the butter and the remaining olive oil on medium heat.
Add the spaghetti squash strands, grated nutmeg, basil pesto, remaining salt, and pepper. Cook, stirring occasionally for 5 minutes.
Reduce the heat to low. Stir in the heavy cream, and Parmesan cheese.
• Cook an additional 2 - 3 minutes and spoon the pesto spaghetti squash into a prepared carved and roasted pumpkin (optional), OR spoon into a bowl and serve warm.