Add oil to a large pot or dutch oven set over medium heat. Once oil is hot, add diced onions, salt, and pepper and cook for about 3 minutes, until onions are just starting to soften.
Add in carrots and cook for another 5 minutes, until onions are starting to brown. Stir in garlic and cook for another minute.
Stir in potatoes, lentils, thyme, cinnamon, nutmeg, and chicken broth. Add bay leaves. Bring to a gentle boil.
Cook, stirring occasionally, until lentils and potatoes are softened, about 35-40 minutes. Remove bay leaves.
Taste and add additional salt and pepper or other spices if necessary and serve soup in bowls topped with parsley.
Optional: If you want a creamier soup, you can remove 2 cups of lentil soup from pot and add it to a blender to puree before stirring it back into the rest of the soup.