Heat oil in a pot, braise the leeks until softened.
Add the diced carrot and mushrooms, stir and braise them too. Pour in the rice and fry until it turns transparent - about 2-3 min.
Add the olive pieces and leave for 5 min. on low heat for the rice to swell. Transfer to a tray, pour in a little more warm water.
Taste it and if needed add some more salt and spices. Bake in a preheated 356°F (180 °C) oven about 30 min. or until the rice absorbs the water. Serve warm.