Rinse the lentils thoroughly under cold water, removing any small stones or debris. Peel and dice the carrots, finely chop the onion, mince the garlic, and dice the celery.

Heat 1 tablespoon olive oil in a large heavy-bottomed saucepan or Dutch oven over medium heat until shimmering.

Add the chopped onion and a pinch of salt. Sauté for 5–7 minutes until the onion is translucent and starting to soften.

Add the diced carrots and celery. Cook, stirring occasionally, for 5 minutes until they begin to soften.

Stir in the minced garlic, ground cumin, dried thyme and smoked paprika. Cook for 30–45 seconds until fragrant, taking care not to burn the garlic.

Add the rinsed lentils, vegetable stock, and 1 cup water. Stir to combine, then add the bay leaf, 1 teaspoon salt, and 1/2 teaspoon black pepper.

Bring the pot to a gentle boil, then reduce heat to low, cover partially, and simmer for 25–30 minutes, or until the lentils and carrots are tender. Stir occasionally and add a splash more water if the soup becomes too thick.

Remove from heat. Discard the bay leaf. For a smooth, velvety soup, use an immersion blender to purée the soup until smooth. Alternatively, carefully transfer batches to a blender and purée, then return to the pot. If you prefer a chunkier texture, purée only half the soup and stir the remainder back in.

Stir in the lemon juice and adjust seasoning with additional salt and pepper to taste (about another 1/2 teaspoon salt if needed). Keep warm over very low heat while you prepare the basil oil and garnishes.

Basil oil

While the soup simmers, make the basil oil so the flavors meld. Blanch the basil leaves in a pot of boiling water for 10 seconds, then plunge immediately into an ice bath to retain bright color (optional but yields greener oil). Pat basil leaves dry with paper towels.

In a small blender or food processor combine the blanched basil, 1/2 cup extra-virgin olive oil, and 1/4 teaspoon salt. Blitz until very smooth, about 30–45 seconds. If you prefer a very bright green oil, strain through a fine mesh sieve or chinois, pressing down to extract as much oil as possible. Alternatively, skip the strain for a more textured oil.

Taste and adjust seasoning. Transfer basil oil to a small pouring vessel and set aside at room temperature. If making ahead, refrigerate and bring back to room temperature before using (oil may solidify slightly when cold).

Garnish / Finishing

Ladle the hot lentil and carrot soup into warmed bowls (about 1 to 1 1/4 cups soup per serving).

Dot each bowl with about 1 tablespoon crème fraîche (or vegan alternative). For a pretty finish, place the crème fraîche in the center and use the back of a spoon to gently swirl a shallow well.

Drizzle about 1 teaspoon of basil oil over each bowl, making 3–4 thin streams or a small pool beside the crème fraîche. Add a small extra drizzle of olive oil if desired.

Finish with a pinch (about 1/8 teaspoon) of finishing salt and a grind of cracked black pepper over each bowl. Scatter a few fresh basil leaves on top for color.

Serve immediately with crusty bread if desired.