Cut the top of the peppers and cut them into thick slices.
Place the oil, garlic and peppers in a large pot. Sauté for 2 minutes, or until the peppers have softened, and then add the vinegar and salt.
Cover the pot, bring the mixture to a boil, and then reduce heat to a simmer for 10 minutes.
Remove the pot from the heat, and let cool slightly. (Use caution when removing the lid from the pot - the steam that comes out will burn your eyes.)
Pour the mixture into a blender, and blend until liquified.
Strain through a fine mesh sieve, and store the liquid in a bottle or jar. It should last a couple of months in the fridge.