Peel the garlic and roughly chop it with the chilli pepper. Simmer with a little water in a saucepan until the garlic is soft. Pour in a little more water if necessary. Then puree with a hand blender and, if necessary, some oil.
In the meantime, stir the other ingredients together. Then fold in the garlic chilli mixture and season with salt, pepper and herbs.
The sauce keeps for many weeks in a screw-top jar in the refrigerator and is wonderfully suitable as a dip or marinade and tastes wonderful with grilled food.