Use a tissue or kitchen towel to gently remove the dirt from the mushrooms.

Finely chop the onion and mushrooms. You can also use a food processor to pulse in batches, but roughly chop them to similar sizes first. Take care not to over process, so that the mushrooms and onions don’t turn into a pulp

Finely chop or grate the garlic. Roughly chop the sun dried tomatoes. Rinse the lentils.

Use the oil from the sun dried tomatoes to saute the onion and garlic. Sauté on medium heat until they’re softened and translucent, for about 5 mins.

Then, add the mushrooms and sun-dried tomatoes. Season well with salt and pepper, and sauté until the liquid has evaporated and the mushrooms start to brown and caramelise - about 8- 10 mins.

Meanwhile, boil the kettle and stir two stock cubes through 1L of boiling water.

Preheat the oven to 190C.

Once the mushrooms have started to brown, add the harissa if using, and the tomato puree and plum tomatoes, crushing them into the pan with the back of a fork. Add the lentils, ¾ of the stock, season well with salt and pepper, and stir. Simmer on medium-high for 10 mins with the lid slightly off, to allow some steam out. Stir the pot occasionally.

After 10 mins, add the rest of the stock and stir well. Break up the lasagne sheets into large pieces and add them to the pot, pushing them down so they're submerged.

Cover with the lid and bake in the oven for 30 mins.

Remove the pot from the oven and give everything a good stir.

Check that the pasta and lentils have cooked through. The lentils should have a firm bite but not taste powdery or tough. (If they need a little more time, add a splash of water and put the pot back into the oven, for 5-10 more minutes.)

Sprinkle the cheese over the top and close the lid again. Return to the oven for 10 minutes so that the cheese can melt.

Then, remove the lid and place under the grill for a few minutes to crisp up the top, keeping a close eye to prevent it burning.

Let the lasagne rest for 5-10 minutes before serving.