Preheat the oven to 180°C.

Put the potatoes in a large pot and fill with cold water. Bring to the boil, turn down the heat and simmer until fork tender.

Meanwhile, heat one tablespoon of the oil in a large pot and brown half the meat over medium-high heat, setting the meat aside in a bowl once it's done. Wipe the pot to remove any remaining bits of mince, then add the second tablespoon of oil and brown the second batch, adding it to the bowl when it's done.

Wipe down the pot again then add the remaining two tablespoons of oil with the onion and a pinch of sea salt. Cook the onion over low heat for five or so minutes, until it's soft and translucent. There will be some brown bits on the bottom of the pot from the meat and that's OK — that's where good flavour lies. If it looks like it's about to burn, you can deglaze the pan with a bit of stock (or wine, if you have any on hand).

Add the garlic and cook for a couple of minutes, until fragrant, then add the tomato paste and cook for a further minute. Add the flour and stir through, before turning up the heat and adding the celery and carrot. Give everything a good stir to combine, then add the mince back to the pot and lentils if you're using them, along with the broth, bay leaf and pomegranate molasses. Simmer over low heat for 15 minutes (tasting towards the end and adding any salt and pepper, as required).

Once the potatoes are cooked, strain them then put them back in the large pot, along with the butter and parmesan. Mash the potatoes until the butter and cheese melt, then add the creme fraiche and continue mashing until your desired consistency (I tend to do a quick, rough mash most of the time). Taste and season with salt as required (the amount you need will depend on how salty your filling is).

Spoon the mince mixture into a large baking dish (one you would use to make lasagne) and add the mash topping, spreading it out evenly as you go. Drizzle with extra virgin olive oil and place the baking dish on a tray to catch any eager mixture that may escape out the sides. Bake, uncovered, for 30-40 minutes, until the top is golden and the brothy mixture bubbles up the sides.

Allow the pie to sit in the pan for 10 minutes before serving, scattering parsley over the top. Serve with spinach leaves, broccoli or peas.