Peel and thinly slice the yellow onions into half-moon slices so they measure about 3 cups. Smash the garlic cloves with the side of a knife and leave whole.

Sweat the onions

In a 3-quart saucepan or medium stockpot, heat the butter and olive oil over medium heat until butter melts and begins to foam. Add the sliced onions and a pinch of salt. Cook, stirring often, for 8–10 minutes until the onions are soft and translucent but not browned. The goal is a clear, sweet onion base rather than caramelization.

Add garlic and deglaze

Add the smashed garlic cloves and cook 30–45 seconds until fragrant. Pour in the white wine (if using) and scrape any bits from the bottom of the pan. Let the wine reduce for about 1 minute.

Simmer the broth

Add the chicken or vegetable stock (32 oz), bay leaf, thyme sprigs, soy sauce, sea salt, and black pepper. Bring to a gentle simmer over medium-high heat, then reduce heat to low and partially cover. Simmer gently for 15 minutes to allow flavors to meld without turning the onions opaque or cloudy.

Clarify and strain

Remove from heat. Using a slotted spoon, remove and discard the bay leaf, thyme sprigs, and garlic cloves. For a clearer liquid, strain the soup through a fine-mesh sieve or cheesecloth into another pot or large bowl, pressing gently on the solids to extract flavor but not cloud the broth. Taste and adjust seasoning with additional salt or pepper as needed.

Finishing & Garnish

Return the strained clear onion broth to low heat. Stir in the chopped parsley and sliced chives. If desired, add 1 teaspoon lemon juice to brighten the flavor. Warm gently for 1–2 minutes without boiling.

Ladle the clear onion soup into a warmed 32 oz (approx. 4-cup) serving bowl or divide into individual bowls. Garnish with a few extra parsley leaves or a light sprinkle of chives and serve immediately.