Equipment
Ingredients
Aromatics and Base
- 30 g unsalted butter
- 1 yellow onion, diced
- 2 garlic, minced
- 1 russet potato, peeled and diced
Liquids and Greens
- 750 ml vegetable broth, hot
- 2 butterhead lettuce, roughly chopped
Finishing and Seasoning
- 60 ml heavy cream, room temperature
- 15 ml lemon juice, freshly squeezed
- 5 g fine sea salt
- 2 g black pepper, freshly cracked
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 176 kcal
- Protein
- 3 g
- Carbohydrates
- 16 g
- Fat
- 12 g
- Fiber
- 2 g
- Sugar
- 4 g
- Sodium
- 1066 mg
- Saturated Fat
- 7 g
- Trans Fat
- 0 g
- Monounsaturated Fat
- 3 g
- Polyunsaturated Fat
- 1 g
- Cholesterol
- 33 mg
- Potassium
- 464 mg
- Calcium
- 64 mg
- Iron
- 1.6 mg
- Magnesium
- 27 mg
- Phosphorus
- 77 mg
- Zinc
- 0.5 mg
- Vitamin A
- 264 mcg
- Vitamin C
- 11 mg
- Vitamin D
- 0.2 mcg
- Vitamin E
- 0.5 mg
- Vitamin K
- 79 mcg
- Vitamin B6
- 0.3 mg
- Vitamin B12
- 0.0 mcg
- Thiamin
- 0.14 mg
- Riboflavin
- 0.12 mg
- Niacin
- 0.9 mg
- Folate
- 69 mcg
- Water
- 333 g
Sources: USDA FoodData Central
Method
Melt the butter in a large pot over medium heat. Add the diced onion and minced garlic. Cook, stirring frequently, until the onions are completely translucent and soft, but not browned.
Add the diced potato and hot vegetable broth to the pot. Bring the liquid to a gentle simmer around 95 degrees C or 203 degrees F. Cover partially and cook until the potato is completely tender and breaks apart easily.
Stir the roughly chopped lettuce into the simmering broth. Cook very briefly, just until the leaves have wilted and turned a vibrant, bright green. Remove the pot from the heat immediately to prevent overcooking.
Using an immersion blender, puree the soup directly in the pot until it is completely smooth and velvety. If using a stand blender, carefully blend in batches and return to the pot.
Stir in the heavy cream and fresh lemon juice. Taste the soup and adjust the seasoning with the sea salt and freshly cracked black pepper. Ladle into warm bowls and serve immediately.
Chef's Notes
- To achieve a restaurant-quality silky texture, you can pass the blended soup through a fine mesh sieve or chinois before adding the cream.
- The lemon juice is crucial here; lettuce can taste flat when cooked, and the acid brings brightness and dimension to the finished dish.
- For an extra layer of flavor, consider garnishing the soup with homemade croutons or a sprinkle of toasted pine nuts for textural contrast.
Storage
Refrigerator: 3 days — Store in an airtight container. The green color may dull slightly over time.
Freezer: 1 month — Freeze without the heavy cream. Stir in fresh cream after thawing and reheating.
Reheating: Reheat gently on the stovetop over low heat. Do not let it boil vigorously once the cream is added.
Troubleshooting
Soup has a dull, muddy olive green color
Cause: The lettuce was boiled for too long, destroying its natural chlorophyll
Fix: Cannot be fixed visually, but adding a little extra lemon juice can help brighten the flavor profile
Prevention: Add the lettuce at the very end of the cooking process and remove from heat as soon as it wilts
Soup consistency is grainy or watery
Cause: Potatoes were not cooked long enough before blending, or wrong type of potato was used
Fix: Simmer the pureed soup over low heat for another 5 minutes to help the starches hydrate, adding a splash of broth if it gets too thick
Prevention: Ensure potatoes are completely soft and yielding before blending; use starchy potatoes like russets
Cultural Context
Known in classical French culinary repertoire as Potage a la Laitue, lettuce soup originated as a frugal and elegant way to use overgrown or slightly wilted greens from the garden. It transforms a delicate salad leaf into a comforting, restorative bowl that celebrates the transition from spring to summer.
