Preheat the oven to 350°F. Peel away the loose outer papery skin from the garlic heads, leaving the heads intact. Set them in a lightly greased shallow pan and roast for 1 to 1 1/2 hours, until the cloves feel tender when pierced with a knife.

Take the garlic out of the oven and let it cool for about 20 minutes, or until you can handle it comfortably. Separate the heads into cloves, then peel away the skins. Set the peeled cloves aside.

Melt the butter in a large saucepan over medium heat. Stir in the flour and cook until the mixture foams. Gradually whisk in the chicken broth, then bring it to a boil. Add the salt, freshly ground white pepper, dried thyme, and peeled garlic. Lower the heat and simmer uncovered for 10 minutes.

Remove the saucepan from the heat and let the soup cool slightly if you plan to use a countertop blender. Blend the mixture in batches until smooth, or use an immersion blender in the saucepan. Return the soup to the pan if needed, then stir in the cream.

Warm the soup over medium heat, stirring often, but do not let it boil. Ladle it into bowls and top generously with toasted croutons and a sprinkle of paprika. Serve right away while the croutons are crisp.