Especially amazing on summer corn
In a medium heavy-bottom saucepan, heat the oil to 350F. Make sure to use a pan that is big enough to fry your chiles without crowding them. The oil should be 1 to 2 inches deep.
To test whether the oil is hot enough use a thermometer or place a wooden spoon in the oil and see if tiny bubbles gather around the wood.
Add the dried chiles and fry for 3 to 4 minutes, until they puff up and turn the color of dark chocolate. Once they're done, turn off the heat under the pan, remove the chiles with a slotted spoon, and place them in the bowl of a food processor or in the jar of a very powerful blender.
Immediately drop all of the garlic cloves into the same hot oil used to fry your chiles. Even though the stove is off, the oil should still be very hot, and you will see a commotion of bubbles as the garlic is submerged in it. The cold garlic will begin to lower the temperature of the oil.
Let them simmer in it for about 10 minutes, watching to make sure there are always small bubbles rising in the pot but that it's not frying at a raucous boil. You may need to turn your stove back on to the lowest possible heat setting if the bubbles come to a stop.
You want the garlic to get super-soft and stay fairly light in color, not turn a dark brown so that you get a custardy, roasted garlic texture and a taste that is not bitter but sweet. To test for doneness, use a slotted spoon to remove one of the fried cloves of garlic from the oil. When you press on it with the back of a spoon, it should mash easily. Once the garlic has reached this texture, use the slotted spoon to remove them from the oil (reserving the oil) and place them in the food processor or blender with the chiles.
Add the piloncillo or brown sugar and the salt.
Preheat the oven to 350F. Place the walnuts on a baking sheet, in a single layer, and lightly toast for 5 minutes. You only want to activate the oils, not darken the walnuts, or they will become bitter.
By the time your walnuts have toasted, the reserved oil will have cooled to a temperature where you can handle it. Add the walnuts to the food processor or blender, then puree while slowly adding between ¾ and 1 ½ of the reserved oil in a thin stream.
Blend until it seems as if it can't get any smoother. You want a dark paste that is as uniform as possible.
Transfer to a container with a tight-fitting lid and refrigerate overnight or for up to 24 hours before using so that any remaining chile bits soften. Because the garlic has been covered in oil, this salsa will keep in a sealed container in the refrigerator for up to 3 months. You can also freeze it for up to 6 months.