Heat olive oil in a saucepan. Add the leeks and cook over medium heat, about 3 minutes.
Add broccoli stems and stock. Season with salt and pepper and bring to a boil.
Cover and simmer until the stems are tender, about 20-30 minutes. Add the spinach and let it cook with its proper heat.
Blend it, correct thickness with a bit more stock if necessary and add cream, keeping some for serving.
Serve it with a splash of cream and if using with some cooked lentils.