Gather and prepare your ingredients. Preheat the oven to 200°C/180°C fan.

Heat the olive oil (for the lentils) in a large heavy-bottomed pan over medium-high heat. Add the onions, celery and carrots with a sprinkle of salt and pepper. Cook, stirring often, for 7-8 minutes until softened, darkened and reduced.

Add the garlic, tomato puree, paprika and thyme and cook for 2-3 minutes, until darkened.

Add the tamari, bay leaf, lentils and vegetable stock. Bring to a simmer and cook for 20-25 minutes until the lentils are tender and have absorbed most of the liquid. Adjust seasoning to taste.

While the lentils are simmering place the potatoes in a saucepan and cover with cold water. Add a sprinkle of salt and place over medium heat. Bring to a simmer and cook for 17-20 minutes, until tender. Drain well.

Allow the potatoes to sit in the colander for several minutes to steam. The drier your potatoes at this stage, the creamier your mash will be.

While the potatoes are draining place the pan back over the heat. Add the olive oil with the milk. Heat for 2-3 minutes, just until shivering but do not let it bubble.

Turn off the heat and place the cooked potatoes back into the pan. Mash until creamy. Stir through the basil and add salt and pepper to taste.

Pour the lentils into a 24x30x5cm baking dish and top with the mashed potatoes. Bake for 30-35 minutes, until golden brown and bubbling. Allow to cool for 5 minutes before serving.