Preheat oven to 475 degrees.
1. Cut top of garlic head, leaving the whole head intact but exposing the tops of the cloves and place on one half of a baking sheet along with acorn squash chunks and red onion. On the other half of the baking sheet, place the potatoes. Drizzle everything with olive oil and season with salt and pepper. Roast in the oven, checking and turning occasionally.
(Remove veggies as needed: garlic when the tips of cloves start to brown, potatoes when they can be pierced with a fork but are still quite firm and squash when soft and browned. Set all veggies aside to cool).
Prepare collard leaves
2. Place tamale pot or steamer pot with water over medium-high heat and bring to simmer. Meanwhile, trim collard leaves by cutting along the edge of stem and removing the thickest parts, but leaving the top 3-4 inches intact so that your leaves are still held together. Steam trimmed leaves for about 5 minutes and set aside.
Prepare tamale dough
3. In a small saucepan over medium heat, warm but don’t boil 2 cups of vegetable stock. While the stock warms, in a medium bowl combine solid coconut oil and all of the roasted garlic cloves (cooled and peeled). Mash with a fork to combine. If the oil starts to liquefy, chill it in the fridge for a bit. Then add masa flour in batches to the coconut oil using a fork or side of a wooden spoon, until mixture resembles large crumbs.
4. Ladle vegetable stock into masa mixture a little at a time, mixing until the dough is smooth and spreadable. Cover dough and set aside. Then combine filling ingredients: place cooled squash and onions in a bowl and mash, cut cooled potatoes into small bite sized pieces and fold into squash; season with cumin and salt and pepper to taste.
Assemble and cook tamales
5. Set steamed collard leaves out on a large work surface. Spread masa dough about ¼-inch thick across top of leaf where the stem is still attached. Then spoon filling onto center of dough.
6. Fold in sides of leaf and roll, tucking in sides as you go so you have a little burrito, place prepared tamales in steamer pot. Steam tamales for about an hour until masa is firm.