Preheat your oven to 375 degrees f. and line a baking sheet with parchment paper.
Carefully cut the butternut squash in half lengthwise; remove and discard the seeds.
Place your squash halves skin side down onto the prepared baking dish. Add the onion next to it and the head of garlic wrapped with a piece of parchment paper as shown.
Spritz with avocado cooking oil spray and season with sea salt and pepper.
Roast for about 30 minutes, or until the squash is fork-tender. The onion might roast faster, so check at about 15-20 minutes and take it out of the oven, leaving the butternut squash and garlic for longer. Sometimes I'll simply tuck the onion inside the squash.
Allow your squash to cool for a bit.
Scoop out the roasted flesh into a food processor together with your roasted onion and garlic cloves (popped out of the skin). You can add all the garlic if you like the flavor or just half of it.
Add in your milk of choice and seasonings then pulse until super smooth. Start with less milk and add slowly until desired "dip" consistency is achieved.
Taste test and season to your taste. Sprinkle with fresh chopped chives if desired.
Serve warm with crunchy veggies to dip. Enjoy!