Step 1 of 4

Cook the base down and brown the mushrooms

Heat the oil in a wide pan and cook the onions, carrots and celery with a teaspoon of the salt for 12 minutes. Add the garlic and mushrooms and cook for a further 8 minutes, until the mushrooms have given up their water and started to brown. Stir in the tomato paste for 2 minutes.

— Wait for the mushroom water to boil away and the pan to sizzle again. That is where the savory depth comes from, and it is the thing a meat-free pie most needs.