Step 1

Place racks in upper and lower thirds of oven; preheat to 450°. Roast tomatoes, tomatillos, onion, and garlic on a rimmed baking sheet on upper rack until softened and browned in spots (vegetables should still hold their shape), 25–35 minutes. Let cool slightly. Cut the top off the garlic, exposing the cloves inside. Squeeze out roasted garlic cloves into a blender. Transfer remaining vegetables to blender and purée until smooth. Scrape into a medium bowl.

Step 2

While the vegetables are roasting, toast ancho and guajillo chiles on a clean rimmed baking sheet on lower rack until guajillo chiles are slightly darker in spots, about 4 minutes. Let cool slightly, then transfer to a large bowl. Add raisins and 4 cups boiling water, cover with plastic wrap, and let sit 30 minutes.

Step 3

Transfer chile mixture to blender (you don’t need to clean it); blend until thick and smooth.

Step 4

As soon as chiles are out of the oven, toast sesame seeds on another rimmed baking sheet on lower rack until golden brown, about 3 minutes. Let cool. Grind in spice mill, shaking occasionally, to a powder. Be careful not to overgrind or you will make sesame paste. Transfer to a small bowl.

Step 5

Very finely grind cinnamon, allspice, cloves, and cumin seeds in spice mill. Heat oil in a large pot over medium-high and cook spice mixture, stirring, until fragrant, about 30 seconds. Add vegetable purée and cook, stirring occasionally, until mixture thickens slightly, 5–7 minutes. Add chile purée and broth, season with salt, and simmer, uncovered, stirring occasionally, until mole is thickened to the consistency of heavy cream, 60–75 minutes.

Step 6

Add sesame powder, chocolate, breadcrumbs, and piloncillo to mole and whisk until chocolate is melted and sesame seeds are incorporated. Continue cooking, whisking often to prevent mole from sticking to the bottom of the pot, until very thick and the consistency of marinara sauce, 30–35 minutes. Taste mole and season with salt as needed.