Soak lentils in cold water for 1 hour. Drain and set aside.
STEP 2
Heat olive oil in a pot over medium heat. Add onion and carrot; sauté until soft, 3 to 5 minutes. Add lentils and bay leaves; stir until coated with oil. Pour in 3 cups of vegetable broth, stir, and bring to a boil. Cook at a slow boil for 10 minutes.
STEP 3
Reduce heat to a simmer; add buckwheat groats. Simmer until lentils are soft but not mushy and buckwheat is cooked, about 25 minutes. Add remaining broth if needed. Stir in spinach until wilted, then remove bay leaves.