For the sauce, heat the ghee in a medium-large deep-sided skillet over medium heat. Once hot, add the onion and cook until softened and starting to caramelize, about 20 minutes, stirring occasionally. Stir in the garlic, ginger, and remaining spice mix and cook 1 minute, stirring constantly. Stir in the salt, crushed red pepper flakes, chicken broth, and tomato paste. Bring up to a boil, and then reduce the heat to simmer and cook 10 minutes. Cool slightly and then carefully puree using an immersion or regular blender. Return the sauce to the skillet.