Heat a 12" skillet, preferably cast iron until hot over medium heat.Add Mulato Chiles and toast 2 minutes on each side, but do not blacken! Cool slightly, remove core and seeds; add the chiles to 1 1/2 cups of boiling water and set aside for 20 minutes. (Wear gloves if you are sensitive to chile heat level.)Drain chiles, keeping the soaking water! Set aside. In the skillet, add 1 tablespoon oil; set to medium heat.Add onion and garlic and cook, stirring until just golden. Add sesame seeds, cumin seeds and oregano; stir and cook 1 minute.Add the chopped tomatoes and cook until they start to just color.Add 1/2 cup tomato juice, and drained soaked chiles and 1 1/4 cups of the reserved chile-soaking water; bring to a boil, then reduce to a simmer.Reduce the heat and cook at a simmer 5 minutes. Add to the carafe of a blender and puree until smooth. Add extra 1/4 cup soaking water if too thick. Use as is, or enrich :Heat 2 tablespoons oil in a large skillet over medium heat. When very hot, add the pureed sauce (will splatter a bit) and cook, stirring consistently until warmed through and only slightly thickened. The Chile Sauce keeps well in a tightly sealed glass container in the refrigerator for up to 4 weeks. Delicious with my Chicken and Veggie Tacos - see recipe!