- STEP 1
Heat 5-6 tablespoons of olive to a large flame-proof casserole and add the onions, carrots and celery. Cook for 5-10 minutes stirring until the onions have softened a little.
- STEP 2
Add the chopped tomatoes, red wine vinegar, season with the salt and plenty of black pepper. Stir well, cover and simmer on the lowest heat for an hour.
- STEP 3
After an hour, turn off the heat and let cool for 30 minutes.
- STEP 4
Stir in the basil leaves and using a liquidiser blend in batches until smooth.
- STEP 5
Divide the sauce into as many 150ml click-lock plastic containers as you can and put them in the freezer. These can then be taken out and defrosted as and when you need them.