Preheat your oven to 400°F (200°C). Trim the top off the whole garlic head, drizzle it generously with olive oil, and wrap it securely in foil. Place it in the oven for 30–35 minutes, until golden, tender, and fragrant.

While the garlic is roasting, grab a large pot and pour in the chicken stock. Add dried sage and a pinch of salt, then bring the mixture to a gentle simmer over medium heat for about 10 minutes.

Once the garlic is cool enough to handle, squeeze the soft roasted cloves into a smooth paste and stir this sweet paste into the simmering stock mixture.

In a separate bowl, whisk together the egg yolk and Dijon mustard. To prevent scrambling, whisk in some hot soup into the mixture gradually before returning it to the pot.

Drizzle in olive oil while stirring, allowing the soup to simmer gently for another 10 minutes. Adjust seasoning with salt and pepper, if necessary.

Ladle the hot soup into bowls, garnishing with fresh herbs or olive oil. Enjoy with rustic bread or salad!