Boil a large pot of water and slice a small 'x' in the bottom of each tomato.
Working in batches, blanch the tomatoes in the pot for about 30 seconds (to loosen the skin place them in a large bowl filled with cold water to cool.
when the tomatoes are cool, peel the skins from the tomatoes. They should peel off easily in quarters from where you made the x.
To cook the sauce:
Chop the tomatoes lightly and place them into a large pot. Bring the tomatoes to a boil then reduce the heat to a simmer.
Simmer the tomatoes for about 30 minutes then puree with an immersion blender. If you are using a stand blender, you will need to do this step in batches.
Add the crushed garlic and basil leaves to the pot and simmer for another 10-15 minutes.