Warm the oil in a large casserole dish saucepan over a medium heat. Add your vegetables and potatoes then fry them over a medium heat, stirring as you go.
Once the vegetables have started to brown and soften add the 3L of stock (if you are using stock cubes/pots that equates to 4 dissolved in 3L of boiling water) along with your fresh, chopped herbs. Cover it with a lid and bring to the boil. Reduce the heat and allow to simmer for 20 minutes until the vegetables are tender.
Five minutes before the end of cooking time, season with freshly ground salt and black pepper.
Finally, use an immersion blender to achieve your preferred smoothness. Spoon into warmed bowls and serve up with a dollop of creme fraiche.