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 and stir until they release a toasty aroma—a minute or two--, then add the vinegar, ¼ cup water and generous ½ teaspoon salt. Stir for a minute or so, then remove from the fire and let cool.
Using an immersion blender (or you can scoop everything into your blender jar), pulse the salsa macha (I use full one-second bursts) until the chiles, garlic and peanuts are in small pieces. It 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 tight-fitting lid and store in the refrigerator.