In a large Dutch oven, simmer chicken stock with fresh sage over medium heat until fragrant and bubbling, about 5 minutes.

In a small pot, boil halved garlic cloves in water for 3-4 minutes, then drain and mash finely.

Stir the mashed garlic into the simmering stock and let it simmer gently for 10 minutes.

In a separate jar, blend the egg yolk, Dijon mustard, and salt. Gradually incorporate the olive oil while whisking until creamy.

For an ultra-smooth texture, strain your soup through a fine mesh sieve and return it to the pot.

Mix a scoop of hot soup into the mayonnaise, whisking until smooth. This prevents curdling.

Gently heat the soup until steaming, avoiding boiling. Serve in bowls with optional toppings.