Chop all the vegetables (except peas) into small cubes.
Fry the chopped onions in the oil, adding in the other chopped veg when they have softened. Cook for a further 5 minutes.
Gradually add 500ml water and your seasonings and cook with a lid on the pan for 15 minutes or until the vegetables are easily speared with a knife. You may need to add more water to achieve the desired texture. (You are aiming for a thick soup)
Then add the peas and blitz in a food processor, liquidizer or with a stick blender.