Heat the olive oil in a small saucepan over a medium heat. Add the sliced garlic and fry gently for 1-2 minutes until it begins to turn golden. Watch carefully as burnt garlic will make the sauce bitter and can't be rescued.
Add the chopped fresh tomatoes and stir to combine with the garlic. Cook for 2 minutes until the tomatoes begin to soften.
Pour in the passata and stir well. Add the whole chilli, leaving it whole so the heat infuses gently into the sauce during simmering. For more heat slice the chilli before adding.
Tear the basil leaves roughly and add to the pan. Season with a pinch of salt and sugar if using.
Bring to a gentle boil, then reduce to the lowest heat and simmer for a minimum of 10 minutes. The longer you simmer the more concentrated the tomato flavour gets. 20 minutes gives an excellent result, 30 minutes is even better.
Remove the whole chilli if used. Push the sauce through a fine sieve to remove any lumps of garlic, tomato skin, basil leaves and chilli. This produces a smooth, glossy sauce. Alternatively leave it chunky if you prefer more texture or blend with a stick blender for a half way house.
Allow to cool slightly before spreading on pizza bases. The sauce should be thick enough to spread without running off the edges.
