How to Make It
Heat a cast-iron skillet. Add the pumpkin seeds and toast over moderate heat until golden, 3 to 5 minutes. Transfer to a small bowl. Heat both oils in the skillet until barely shimmering. Add the chiles and cook until browned in spots. Transfer the oil and chiles to a bowl, add the garlic and let cool.
In a blender, puree the toasted pumpkin seeds with the chile oil, vinegar and piloncillo until very smooth. Season the vinaigrette with salt.
Piloncillo is a pure, unrefined cane sugar from Mexico that’s pressed into a cone shape and grated for use.