Peel your potatoes and cut them into large chunks. Place in a saucepan and cover with cold water.
Place the pan on medium heat and bring to a boil, leaving your potatoes to boil until a knife easily goes through them.
Drain your potatoes and add the butter and milk. Then, mash until smooth and creamy. Season to taste. Set the potatoes aside while you prepare the lentil shepherd’s pie filling.
In a skillet or frying pan, heat your oil and then tip in the onion and carrot.
Saute on low heat for a good 5-7 minutes until the vegetables have softened, then tip in the minced garlic, seasonings, tomato paste, and plain flour. Cook for a further minute.
Pour in the red wine, cook for 2 minutes to allow the alcohol to cook off, then pour in the passata and tamari.
Stir in your green lentils and season with salt and pepper, simmering the mixture for 5 - 10 minutes until the sauce thickens.
Remove the pan from the heat. If you’re not using an oven-safe pan, transfer the lentil mixture into an oven-safe casserole dish. Spoon over the mashed potatoes, and use a fork to create lines in the mashed potatoes (which will turn deliciously crispy in the oven!).
Pop the pan in the oven and bake for 25 minutes, then scatter over the cheese and place under the grill for 5 minutes until golden brown and bubbling.
