In a large Dutch oven, pour in the chicken stock and toss in the fresh sage leaves. Heat over medium until it simmers, about 5 minutes.

While the stock simmers, halve several cloves of garlic, blanch them in boiling water for 3-4 minutes, then mash into a paste.

Stir the mashed garlic into the stock and let it meld with the sage for about 10 minutes.

For mayonnaise, combine egg yolk and Dijon mustard, then slowly drizzle in olive oil while blending until thick.

If desired, strain the soup through a fine-mesh strainer to achieve a silky texture.

Temper the mayonnaise by mixing some hot broth into it, then return it to the pot without boiling.

Gently heat for another 2-3 minutes, then ladle into bowls and garnish as desired.