Mushroom Soup with Winter Vegetables

Roast the garlic: Heat oven to 400°F. Cut about 1 inch off the top of both heads of garlic, dot each with 1 tablespoon butter, wrap in foil, and roast until soft -- about 45 minutes; let cool and squeeze to release the roasted meat. Discard the skins and set meat aside. Make the vegetable stock: Melt 1 tablespoon butter in large saucepan. Add half the onions and cook over low heat until caramelized -- about 25 minutes. Add the mushroom stems, half the carrots, and the celery and cook until soft -- about 10 minutes. Add 8 cups water, parsley sprigs, and bay leaf, increase heat to high, and bring to a boil. Reduce heat to low and simmer for 45 minutes. Strain and discard the solids. Add enough water to bring stock to 6 cups. Set aside. Make the soup: Melt 1 tablespoon butter in a large Dutch oven over medium heat. Cook the mushrooms in thirds, adding an additional 1 tablespoon butter with each batch, until golden -- about 3 minutes per batch. Add the remaining onion and cook until softened -- about 3 minutes. Add the squash and remaining carrots and cook for 2 minutes. Add the red wine, salt, pepper, roasted garlic, and reserved vegetable stock, stir to combine, and bring to a boil. Reduce heat to low and simmer until vegetables are tender -- about 25 minutes. If freezing, skip to Step 4. Stir in chopped parsley and lemon juice and serve immediately. Freeze the soup: Cool soup completely, transfer to an airtight container, and freeze for up to 2 months. To serve, thaw soup in the refrigerator. Place thawed soup in a large saucepan over medium-high heat and bring to a boil. Reduce heat to low and simmer for 5 minutes. Stir in chopped fresh parsley and lemon juice.