Heat the olive oil in a large saucepan and sauté the leeks for 5 minutes over a medium heat until softened.
Add the chopped herbs and cook until wilted – approx. 2 minutes. Add the garlic and sauté gently.
Add the tamarind, smoked paprika, tomato purée, butter and flour and stir until fully incorporated. Add the stock and water at once and season well.
Bring to a boil then add the (strained) lentils. Simmer uncovered over a low heat for 30 minutes or until the lentils are tender.
Season well and serve with the dill sprinkled on top.