Cook the garlic and peanuts. In a medium saucepan, heat the oil over medium to medium-low. Add the garlic and peanuts. Cook gently (it’s more a gentle confit than frying), stirring from time to time, until the garlic is just softening and the peanuts are slightly golden, about 10 minutes, depending on the temperature of your oil.
Add the chiles and sesame. Stir until they release a toasty aroma—a minute or two—then add the vinegar, ¼ cup water and scant teaspoon salt. Stir for a minute or so, then remove from the heat and let cool.
Blend the salsa. Pour everything into a blender jar (or you can use an immersion blender.) Start at low speed to get all the ingredients moving through the blade uniformly. Slowly increase the speed to medium. Check the consistency and blend only until the chiles and peanuts are in small pieces. It should not be puréed, but should be the texture of the chile oil you see on the tables of Chinese restaurants. For long storage, scrape it into a jar with a tight-fitting lid and store in the refrigerator.