Preheat oven to 400F / 205C.
Slice top off garlic bulb, exposing the ends of all bulbs, and pour over 1 tsp olive oil. Rub in very well to make sure all nooks and crannies are coated. Wrap garlic tightly in aluminum foil and place in the oven for 30 minutes.
Meanwhile, in a large pan, add 1 tsp olive oil and the sliced onions and caramelize using vegetable broth. You will add about 1/4 cup at a time and keep adding when things look like they're drying out. Continue this until the onions are caramelized to your liking, usually at least 15 minutes. I prefer to lightly caramelize them for this pizza so don't need much more time than that. The less you stir, the quicker this process will go. Set aside.
Add 1 tsp olive oil to the pan, then add the sliced mushrooms. Season with salt and pepper, then sauté until all of their moisture has released and evaporated and the mushrooms are nicely browned. Add the vegan butter and thyme and stir to combine. Set aside.
Add 1 tsp olive oil to the pan, then spinach and season lightly with salt. Add 1/4 tsp nutmeg and cook until spinach is just wilted. Set aside.
Remove garlic from the oven and let cool slightly, then squeeze the roasted garlic cloves from the skin into a small bowl. Add 2 tsp olive oil and Italian seasoning and mash with a fork until well combined and tapenade has formed.
Pre-cook your crust for 5-10 minutes, then remove from oven to cool and assemble.
TO ASSEMBLE PIZZA: Spread the roasted garlic tapenade over the pizza crust. Next spread over the cheese. Then layer on the caramelized mushrooms, followed by the spinach, and finally the mushrooms.
Cook for 10 minutes in the oven, then switch the oven to broil (HI) and cook for another 5 minutes under the broiler.
Top with chili flakes and serve warm!