1. Heat oven to 375 degrees.
2. Remove loose peel from head of garlic and cut off the top. Place in a square of foil and drizzle with 1 tablespoon of olive oil and arrange 3 sprigs of thyme on top. Gather ends of foil over the top of the head of garlic and place in oven. Roast garlic for 1 hour.
3. Line a baking sheet with foil. Cut onion into quarters. Remove stem and leaves of cauliflower, cut into florets, and toss in large bowl with onion and 1 tablespoon of olive oil.
4. Arrange on prepared baking sheet, season with salt and pepper, and bake for 1 hour.
5. Line another baking sheet with foil. Remove the waxy outer layer of rutabaga and cut into 1-inch cubes. Toss with olive oil and spread on baking sheet. Season with salt and pepper and bake for 30 minutes. When rutabaga and cauliflower are done, then increase oven temperature to 400 degrees for the roasting of the mushrooms (see below).
6. In batches, put cauliflower, rutabaga and roasted garlic cloves in blender with stock and a total of 3 cups of water. When mixture is smooth, pour into a medium pot. Season with salt and pepper, add 2 tablespoon of butter and 1 tablespoon of sherry. Warm on low stirring occasionally to prevent sticking.

For the mushrooms and wilted spinach:

1. While soup warms, prepare mushrooms and spinach. Slice baby bella mushrooms and toss with 1 tablespoon olive oil, 1 tablespoon coconut aminos, 1 teaspoon thyme leaves, salt, and pepper. Roast on a baking sheet in 400-degree oven for 20 minutes.
2. In a skillet, melt 1 tablespoon of butter and add spinach. Season with salt and toss until spinach just begins to wilt.
3. To serve, pour soup into bowls. Float wilted spinach and mushrooms on top of soup in each bowl.