In the pot gently cook the carrots in butter and olive oil.
As you cook the carrots, prepare the other herbs and vegetables then add them in the order indicated in the ingredients list. Stir with a wooden spoon.
When all the vegetables are in the pot, add salt and a few grinds of black pepper, add the lentils and stir.
Then add three or four cups of water. Bring to a gentle boil for 10 to 15 minutes or until lentils are soft.
Keep scraping and stirring with the wooden spoon from time to time. If you are using spinach add it at the simmering stage.
Simmer for five or ten minutes on very low heat.
Add a knob of butter if you like, test seasoning and then rest for 2 to 5 minutes.
I sometimes squeeze a bit of lemon juice in as well to jazz things up.
Serve with a spoonful or two of yoghurt or crème fraîche if you like.