When we lived in Houston we ate often at a restaurant called "Gyro, Gyro". The family that owned it was Middle Eastern and made the most delicious lentil soup I ever tasted. Sadly, the restaurant burned and never re-opened. I have searched and searched for a recipe similar to the one that they used. I have not found anything. As a result, I have written my own recipe. I hope that you enjoy it.
Place beef broth, water, and lentils in a dutch over over a medium heat. Do not cover yet.
Slice onion very thin. Put half of the raw onion into the pot with the lentils.
Put 2 tablespoons of butter and 2 tablespoons of olive oil in a small skillet and heat. Cook the rest of the onion until crispy and add to the lentils and broth. Use a slotted spoon and do NOT add the olive oil and butter to the soup mixture.
Smash the garlic cloves slightly to remove the skin, cut off the stem end and place in soup pot.
Add a 15 ounce can of crushed or diced tomatoes. Do not drain if using crushed. Drain if using diced.
Add 2 whole bay leaves.
Add the remaining 2 tablespoons of butter to the pot.
Add salt and pepper to taste.
Add 10 ounces of frozen spinach to the pot.
Cook on low heat, covered, until lentils begin to soften.
Once lentils have begun to soften, add carrots.
Add very thinly sliced chilis if desired.
Serve using the remaining olive oil, the cilantro, and sour cream, if desired, as garnish.
This is great with crisped pita bread as a side dish. I drizzle mine with olive oil and crisp it in the oven. Then, we dip it into the soup as we eat.