In a 4- to 5-quart pot over medium heat, melt the butter with the olive oil. Add the diced onion, sliced leek and a pinch of salt. Cook, stirring occasionally, until the onion and leek are softened and translucent, about 6–8 minutes. Add the minced garlic, thyme and bay leaf and cook 1 minute more until fragrant.

Seasonal vegetables

add and soften vegetables

Add the diced potato to the pot and stir to coat with the aromatics. Pour in the white wine (if using) and let it reduce for 1–2 minutes. Add the asparagus pieces and peas, then stir for 1–2 minutes to combine. Pour in the vegetable stock and water so vegetables are just covered.

Bring the soup to a gentle simmer, reduce heat to maintain a low simmer, cover partially, and cook until the potato is tender and asparagus is just tender, about 12–15 minutes.

Purée & finish

blend

Remove and discard the bay leaf and thyme stems. Using an immersion blender, purée the soup until smooth or slightly textured, depending on preference. Alternatively, carefully transfer soup in batches to a blender and purée, then return to the pot. If the soup is too thick, add up to 1/2 cup additional water or stock to reach desired consistency.

add greens and cream

Stir in the fresh spinach or baby greens and cook 1–2 minutes until wilted. If using, stir in the heavy cream or crème fraîche and warm through (do not boil).

Seasoning & garnish

Remove the pot from heat. Stir in the lemon juice, salt and freshly ground black pepper. Taste and adjust seasoning as needed.

Ladle the soup into bowls and garnish with chopped chives or parsley and a sprinkle of grated Parmesan if desired. Serve hot with crusty bread.