Blackberries (zarzamoras in Spanish) add subtle tartness to a traditional Mexican mole -- here, served over chicken.
Puree 4 half-pints blackberries, sugar, and 1 cup stock in a blender until smooth. Pass through a fine sieve into a large bowl, discarding solids. Set aside.
Wipe chiles with a damp paper towel. Cut off stems; slit open chiles lengthwise. Remove ribs and seeds; reserve seeds.
Place a small skillet over medium heat; add 3 tablespoons oil. Add almonds and peanuts; cook, stirring, until lightly golden, about 1 minute. Use a slotted spoon to transfer to a medium bowl.
Add pepitas to skillet. Cover; shake skillet until seeds stop popping, about 30 seconds. Transfer to bowl with nuts. Cook pecans until lightly toasted, about 45 seconds. Transfer to bowl. Reduce heat to medium-low. Cook chiles until color darkens slightly, about 20 seconds per side. Transfer to bowl. Cook onion and garlic until lightly caramelized, 3 to 5 minutes; transfer to bowl.
In a small dish, combine sesame seeds, anise seeds, coriander seeds, cinnamon, and 1 tablespoon reserved chile seeds; pour mixture into skillet. Cook until the sesame seeds are lightly toasted, stirring constantly; transfer to bowl. Add clove, cumin seeds, and oregano to the skillet; cook 2 minutes, and transfer to bowl.
Cook the tortilla over a gas burner or under the broiler until toasted, turning frequently with tongs. Remove from heat; crumble tortilla into same bowl. Transfer bowl mixture to a blender, and puree with 3 cups chicken stock until smooth; work in batches if necessary so as not to fill blender more than halfway.
Heat 2 tablespoons oil in a large saucepan over medium heat. Add pureed nut mixture; reduce the heat to medium-low. Cook, stirring, 5 minutes. Stir in blackberry puree; simmer 30 minutes, or until little pools of oil form around bubbles. Season with salt. Remove from heat. Mole can be made up to 2 days ahead; refrigerate in an airtight container.
Season the chicken well with salt and pepper. Heat remaining 1/4 cup oil in a large saute pan over medium-high heat. Working in batches, cook until browned.
Place mole in a large saucepan, and bring to a simmer over medium heat, stirring occasionally. Add the chicken; simmer until cooked through and well coated with sauce. Keep warm until ready to serve. Garnish with remaining 2 half-pints blackberries and oregano.