Step 1

Boil the potatoes until tender, then mash with butter, milk, and salt. You might not need to use all of the milk, so use common sense and see how much you need (this depends on the starchiness of your potatoes, and adding too much liquid will result in a watery mash).

Step 2

Heat oil in a pan, add the onion, carrot, celery, and mushroom. Cook until the vegetables are tender, then add vegetable stock and peas, and garlic. Cook until the garlic is fragrant (about 1 minute) then add the seasonings and flour. Cook for one more minute.

Step 3

Add soy or tamari sauce, lentils, and chopped tomatoes. Cook for 3-4 minutes, then have a taste and see if you need to adjust seasonings.

Step 4

In an ovenproof dish, add the mixture and spread the mashed potatoes over it evenly. Smooth the potatoes out and create a pattern to decorate using the back of a fork (see picture below). Or just create lines and peaks.

Step 5

Bake in the oven for 15 minutes or so at 180°C (356°F), allowing the mixture to bubble. Then lightly brown the top so it's crispy and nice, but be careful as it gets browned pretty quickly.