Bring a large saucepan of water with ½ tsp salt to the boil for the potatoes. 

Trim the carrot, then quarter lengthways (no need to peel). Chop widthways into small pieces. 

Roughly chop the sliced mushrooms. Chop the potatoes into 2cm chunks (peel first if you prefer).

When boiling, add the potatoes to the water and cook until you can easily slip a knife through, 15-20 mins. 

Meanwhile, heat a drizzle of oil in a large frying pan on high heat. Once hot, add the chopped carrot and stir-fry for 3-4 mins. 

Add the mushrooms to the pan and season with salt and pepper. Fry, stirring occasionally, until the veg has softened, 5-6 mins.

In the meantime, peel and grate the garlic (or use a garlic press). Drain and rinse the lentils in a sieve. Grate the cheese.

Once the veg has softened, add the garlic and cook for 1 min. 

Add the passata, mushroom broth paste, red wine stock paste, dried rosemary, sugar and water for sauce (see pantry for both amounts) to the pan.

Bring to the boil, then stir through the lentils. Lower the heat and simmer until thickened, 4-5 mins. 

Once the potatoes are cooked, drain in a colander and return to the pan, off the heat.

Add half the butter (see pantry for amount) and a splash of milk (if you have any) and mash until smooth. Season with salt and pepper.

Preheat your grill to high.

Once the pie filling has thickened, taste and season with salt and pepper if needed. Transfer to an appropriately sized ovenproof dish. 

Top the pie filling with an even layer of mash and sprinkle over the cheese.

Grill until the cheese is bubbling and golden, 5-6 mins.

Meanwhile, clean the (now empty) frying pan and pop back on medium heat with the remaining butter. 

Once melted, add the peas and stir until piping hot, 2-3 mins. Season with salt and pepper, then remove from the heat.

When the pie is ready, serve on plates with the buttery peas alongside.