Tomato and Basil Soup

This soup is easy to make, delicious and a very good way to use the glut of tomatoes we get at this time of year in Spain. I make two versions, one where I roast the tomatoes, onion and garlic and one where I don't roast. 
This recipe will make a generous portion for 4 people or enough for 6 as a starter. Use the best quality tomatoes you can find. Also, it freezes really well and it's simple to make larger quantities.
I always use skinned tomatoes but you can keep the skins on if you prefer. To skin just put the whole tomato in boiling water for a minute then take out and put into cold water to cool enough to handle, the skin will slide off. If you've roasted the tomatoes the skin will fall off easily once cooled enough to handle.
Non-Roasted Version
1 kg tomatoes (skinned)
1 medium onion finely chopped
3-6 cloves of garlic finely chopped (I like lots of garlic but use as much or as little as you like)
knob of butter 
1 tblsp extra virgin olive oil
1 good quality vegetable stock cube made up to 1 litre of stock
1/2 tub natural yoghurt
1 heaped tsp sambal badjak
1 tsp fresh lightly ground cumin
1/2 tsp fresh ground mixed pepper 
small handful fresh basil, chopped
salt to taste
Method
put butter and oil in a heavy bottomed saucepan on a medium heat. Finely chop the onion and garlic, add to the pan, stir to coat with oil and butter and cook until soft (around 7-10 minutes), after skinning the tomatoes, chop them retaining as much juice as possible then add tomatoes and juice to the pan, add the sambal, cumin and pepper, stir and after 2 minutes or so add the vegetable stock. Let everything simmer for 10-15 minutes, take off the heat and blend, put the soup back into the pan and taste, add salt if you think it needs it, add the yoghurt and basil and cook for 2 minutes on a low heat. Serve with crusty bread.