Heat an oven proof pot on the stove top and preheat your oven to 200C (400F).

Add butter and onion and cook stirring every now and then until the onion is soft, about 10 minutes.

Add the stock and lentils. Bring to a simmer on the stove top.

Season and cover with a lid or some foil. Bake for 15 minutes or until the lentils are super soft.

Stir in the parmesan and serve with a green salad on the side.