Carrot and Coriander Soup

This recipe seems pretty apt now that I've seen my second tutor group right the way through their A-levels as it's from my Fiona Beckett student cookbook, which my Dad bought me nearly 10 years ago when I was preparing to leave home and go to university.
Now that I am going back to work, I need to take control over my diet once again and last time I made this, eating it in conjunction with no snacks and a balanced meal in the evening, I lost 5 pounds in a week. That would make going back to work a little easier for me.

Ingredients:
1 white onion
350g carrots, peeled and cut into rounds
2 sticks celery (you can't taste it, I promise!)
1 medium-sized potato
750ml vegetable stock
1 tsp ground coriander
Salt and pepper, to taste

Instructions:
1. Dice the onion and cook on a low heat in Fry Light (or oil/butter depending on your preference) for 5 minutes, until soft.

2. Add the carrots, celery and potato to the pan and stir well. Cover the saucepan and cook for 10 minutes.

3. Add the stock and on a high heat, bring to the boil. Turn the saucepan down to a medium heat and continue to cook for 25-30 minutes until the veggies are soft. Allow to cool slightly (you don't want to melt the blender - that's happened to my Mum before now!).

4. Using a blender, blitz the soup until smooth and return to the saucepan, reheating slowly. Add a little extra water if required, and season to taste.