Equipment
Ingredients
Aromatics and Base
- 15 ml olive oil
- 1 yellow onion, diced
- 3 garlic, minced
- 15 g fresh ginger, peeled and finely grated
Spices
- 4 g ground cumin
- 3 g ground coriander
- 2 g ground turmeric
- 1 g red chilli flakes
Bulk Ingredients
- 500 g sweet potato, peeled and cut into 2cm cubes
- 150 g red split lentils, rinsed thoroughly in cold water and drained
- 1000 ml vegetable stock, hot
Finishing
- salt
- black pepper
- 15 ml lemon juice, freshly squeezed
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 313 kcal
- Protein
- 14 g
- Carbohydrates
- 58 g
- Fat
- 5 g
- Fiber
- 9 g
- Sugar
- 8 g
- Sodium
- 1124 mg
- Saturated Fat
- 1 g
- Monounsaturated Fat
- 3 g
- Polyunsaturated Fat
- 1 g
- Potassium
- 908 mg
- Calcium
- 97 mg
- Iron
- 4.8 mg
- Magnesium
- 63 mg
- Phosphorus
- 191 mg
- Zinc
- 1.8 mg
- Vitamin A
- 893 mcg
- Vitamin C
- 12 mg
- Vitamin E
- 1.2 mg
- Vitamin K
- 7 mcg
- Vitamin B6
- 0.6 mg
- Thiamin
- 0.46 mg
- Riboflavin
- 0.18 mg
- Niacin
- 1.9 mg
- Folate
- 202 mcg
- Water
- 141 g
Sources: Aggregated Public Data, USDA FoodData Central
Method
Heat the olive oil in a large saucepan or Dutch oven over a medium heat until shimmering.
Add the diced onion to the pan and cook for 5 to 7 minutes, stirring occasionally, until softened and translucent.
Stir in the minced garlic, grated ginger, cumin, coriander, turmeric, and chilli flakes. Cook for 1 minute until highly fragrant.
Add the cubed sweet potato and rinsed red lentils to the pan, tossing them in the spiced onion mixture. Pour in the hot vegetable stock and bring the liquid to a rolling boil at 100 degrees Celsius or 212 degrees Fahrenheit.
Reduce the heat to medium-low, partially cover the pan with a lid, and allow the soup to bubble gently for 20 to 25 minutes.
Remove the pan from the heat. Carefully submerge the immersion blender into the liquid and process until completely smooth and velvety.
Taste the soup and stir in salt, freshly ground black pepper, and the fresh lemon juice if using. Ladle into warm bowls to serve.
Chef's Notes
- Always rinse red split lentils thoroughly under cold running water until the water runs clear. This removes natural saponins and dusty residue which can make the soup foam excessively or taste mildly bitter.
- Do not skip the step of blooming the spices in the hot oil. Fat-soluble flavor compounds in the cumin, coriander, and turmeric open up dramatically when toasted, resulting in a deeper, more complex final bowl.
- The squeeze of fresh lemon juice at the end is technically optional but highly recommended. Earthy ingredients like sweet potato and lentils can taste flat without a hit of acid to provide balance and high notes.
- This recipe benefits significantly from resting. Making it a day in advance allows the spices to meld and intensify. It will thicken in the fridge, so be prepared to loosen it with a splash of water upon reheating.
Storage
Refrigerator: 4 days — Store in an airtight container. The soup will thicken as it cools.
Freezer: 3 months — Leave 2cm of headspace in the container as the liquid will expand when frozen.
Reheating: Reheat gently in a saucepan over medium-low heat. Add a splash of water or vegetable stock to loosen the consistency if it has thickened during storage.
Troubleshooting
Soup is too thick and resembles a puree or mash rather than a liquid
Cause: The red lentils absorbed more liquid than anticipated or the soup simmered too vigorously causing excessive evaporation
Fix: Stir in additional hot water or vegetable stock in 50ml increments over low heat until the desired consistency is reached
Prevention: Ensure the pan is partially covered during the simmer phase to trap moisture
The soup tastes bland despite following the spice measurements
Cause: The vegetable stock lacked adequate sodium or the spices were stale
Fix: Add more salt in small pinches, and stir in the optional lemon juice. Acid brightens earthy root vegetables and amplifies existing flavors
Prevention: Use fresh spices and a high-quality, flavorful vegetable stock
Cultural Context
While the combination of lentils and warming spices draws heavy inspiration from South Asian dal and Middle Eastern cooking, this specific iteration of spiced root vegetable and lentil soup has become a modern British staple. It is a fixture in contemporary cafes and home kitchens across the United Kingdom, celebrated as an affordable, hearty, and deeply comforting remedy to cold, damp winter weather.
