Boca Negra with Tomatillo Sauce (Flourless Chocolate Cake)

Ingredients

• 12 tablespoons (1 ½ sticks) unsalted butter or nondairy butter, cut into small pieces, plus 1 teaspoon for the pan
• 1 cup plus 1 tablespoon sugar
• 6 medium dried chipotle chiles
• 10 ounces high-quality semisweet chocolate, finely chopped
• 6 tablespoons fresh orange juice
• 4 large eggs
• 1 ½ tablespoons cornstarch or almond flour
• Pinch of kosher salt
• 1 pound tomatillos, husks removed, rinsed and coarsely chopped
• 1 vanilla bean, split lengthwise
• 8 ounces piloncillo (see headnote)
• ¼ cup sugar
• ⅓ cup water
• 1 small cinnamon stick