I take no issue at using the peeled garlic available at many stores. Just make sure it is as fresh as possible.
25 peeled cloves of garlic, from about 2 heads
2 medium leeks, white parts only
1 small white onion
3 large green onions, white and lightest green part only
7 cups of chicken broth
1 cup heavy cream
Salt to taste
1. Preheat the oven to 350 degrees F.
2. Place the garlic in a large, oven-proof Dutch oven (about 5 quarts). Slice the leeks in half, rinse them under running water, cut into chunks and add to the pot. Cut the onion into chunks and add to the pot, then cut the green onions into pieces. Salt them lightly, then pour in 2 cups of chicken broth and stir.
3. Place the pot in the oven, uncovered. Roast the vegetables for 1 hour, stirring occasionally, until everything is soft and mushy and the liquid is reduced. Remove from the oven and leave to cool a few minutes.
4. Transfer the vegetables and liquid to a blender and add 1 cup of chicken broth. You may want to do this in batches. Very carefully purée the soup. Leave the hole on the cover of the blender open, but hold it down with a tea towel. Hot liquids tend to send the cover flying. Wipe out the pot.
5. Pour the purée through a strainer and scrape as much substance through it as possible. Discard any leftover bits. Stir in the remaining 4 cups of broth and bring to a boil. Reduce the heat, cover the pot and simmer for 45 minutes. Pour in the heavy cream and whisk to combine. Cook gently until the soup is warmed through.
6. The soup will keep, covered, in the fridge for two days. Reheat gently to serve, do not boil.