Boil the potatoes for the topping, then mash with olive oil, plenty of salt and a splash of the cooking water. Keep it stiff — loose mash sinks into the filling.

Brown the finely chopped mushrooms hard in a dry pan first, until they squeak and colour. Do not add oil until the water has driven off.

Add oil, the diced onion and carrot, and cook 10 minutes.

Add the tomato paste and fry for 2 minutes until it darkens, then the lentils, thyme and broth.

Simmer 25 minutes until the lentils are soft and the mixture is thick — not soupy, or the topping will sink. Stir in the peas.

Spread the mash over, rough up the surface with a fork, and bake at 200C / 180C fan for 25 minutes until the peaks are browned.