How to cook
Chop the onion finely. Peel the zucchini and cut them into medium-sized bites along with the mushrooms (they shrink a lot later - especially the mushrooms). Dice the pepper. Wash the rice.
Heat oil in a tray, braise the onion, pepper and the mushrooms in it. Then put a lid on and leave them at a lower heat until the mushrooms soften a bit, while stirring from time to time so they don't stick.
Once the rice has absorbed most of the water, add the tomato paste and salt to taste. Leave to simmer until ready.
If the rice ends up a little too watery, it will thicken a bit by the next day or a little later.