Peel the vegetables and dice them (roughly). Put in a large pressure cooker a drizzle of extra-virgin olive oil, the vegetables and the herbs: stir and cook for about 10 minutes to mix all the flavours (if necessary, add some water). Now, Pour in water (about 2l) to cover the vegetables, add a drizzle of oil and, if you want to, a stock-cube (season with salt consequently). Close the pressure cooker, and cook on high heat for about 30 minutes from the whistle. Let the soup cool down, then purée with a hand mixer. I love this soup even "pure", with some parmesan cheese only, but its variations are unlimited: often I add some croutons (dry home made bread diced, seasoned with oil, salt and rosemary and baked in the oven), sometimes I put a spoon of cream in the middle of the dish. To obtain a more nourishing dish, you can add some pasta or some cereals (previously cooked -firm- or uncooked), especially pearl barley: it's fantastic, because it's rustic, crunchy, nourishing, but still light.