If your pressure cooker has a sauté setting, you can use this to brown the onion and vegetables before adding the water, otherwise, you can throw all the vegetables into your pot, cover with water and seasoning and place the lid on. Use the setting for soup/stew and press start!
If you don't have a pressure cooker, you can sauté the onion in the oil, add the rest of the vegetables, cover with water and add salt. Bring to the boil and then turn down the heat and allow the soup to simmer for 20 minutes!
An easy and simple recipe to make and once the soup has cooled down, you can place it in a sealed container and keep it in the fridge for up to 4 days.