Heat the olive oil in a large pot over medium heat.
Add the diced onion and cook until soft and translucent, about 5–7 minutes.
Stir in the garlic, bay leaves, fennel seed, and nutmeg, and cook for another 1–2 minutes until fragrant.
Add the potatoes, carrot, turnip, and red lentils to the pot.
Pour in the water or stock (or water plus bouillon cubes) and stir well.
Bring to a boil, then reduce to a gentle simmer.
Cook for about 25–30 minutes, or until the vegetables and lentils are completely soft and starting to break apart. We want everything soft enough that it will puree easily.
If using fresh bay leaves, leave them in (remove dried bay leaves).
Using a stick blender, puree the soup directly in the pot until smooth and creamy.
Taste and season with salt and pepper, adjusting until the base is well seasoned before adding the green beans.
Add the sliced flat green beans to the pureed soup.
Return to a gentle simmer and cook for 10–15 minutes, or until the green beans are tender but not mushy.
If the soup is thicker than you like, we can loosen it with a splash of hot water or stock; if it’s too thin, simmer a bit longer to reduce.
Ladle into warm bowls and finish with a drizzle of olive oil and a crack of black pepper.
This soup holds beautifully for leftovers; the flavors deepen by the next day, making it an easy make-ahead option for cozy lunches or weeknight dinners.