Preheat your oven to 375F and line a large baking sheet with parchment paper. Cut the ends of the spaghetti squash then stand on end to slice in half. Use a spoon to scrape out the seeds. Place the squash halves onto your baking sheet flesh side up, rub the flesh with ghee or avocado oil, and bake for 20 – 30 minutes.
While the squash is cooking bring the water to a boil in a small saucepan. Add the sliced and well rinsed leek to the water, reduce to a simmer, and cook for 10 minutes. Once soft, transfer to a blender with the optional garlic, lemon juice, sea salt, ghee or avocado oil, and plant milk. Blend on high until smooth. Add dashes of black pepper and whiz on low to mix. Taste and adjust as desired.
Add two cups of the cooked spaghetti squash strands to a large bowl along with optional additions: spinach or baby swiss chard, cooked mushrooms, pan-fried lemon chicken or shrimp, baked proscuitto, etc.
Toss the spaghetti squash with the creamy leek sauce, using tongs, or serve on a plate and top with the sauce and additional ingredients.