Preheat your oven to 400°F (200°C). Place the whole garlic head on a baking sheet, drizzle with one tablespoon of olive oil, and wrap loosely in foil. Roast for about 30-35 minutes until soft and fragrant, filling the kitchen with a warm aroma.
While the garlic roasts, trim the dark green tops and roots from the leeks, then slice them in half lengthwise. Rinse thoroughly under cold water to remove any dirt trapped between the layers, then chop into roughly 1-inch pieces.
Heat the remaining tablespoon of olive oil in a large pot over medium heat. Add the chopped leeks and a pinch of salt, then cook gently for about 8-10 minutes until they soften and start to turn translucent, releasing a sweet aroma.
Once the garlic has roasted and cooled slightly, squeeze the softened cloves out of their skins directly into the pot with the leeks. Stir well to combine, allowing the garlic to mingle with the leeks’ sweetness.
Pour in the vegetable broth and add the bay leaf. Bring the mixture to a gentle simmer over medium heat, then reduce the heat to low. Cover the pot partially and let it cook for about 15 minutes to allow flavors to meld.
Remove the bay leaf, then use an immersion blender to blend the soup directly in the pot until smooth and velvety. Alternatively, transfer the mixture in batches to a food processor and blend until creamy.
Taste the soup and season with salt and freshly ground black pepper until balanced. If desired, stir in a splash of olive oil for added richness and shine.
Warm the soup gently for another few minutes, then ladle it into bowls. The soup will be smooth, with a golden hue from the roasting process, inviting a cozy, rustic presentation.
Finish each bowl with a touch of freshly ground pepper or a drizzle of olive oil if you like. Serve hot and enjoy the comforting, mellow flavors of this roasted garlic and leek soup.