In a large bowl, combine the mashed black beans, sugar, ground cinnamon, ground allspice, and vanilla extract. Mix well.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the bean mixture, stirring until a smooth dough forms.
In a small bowl, mix the sweetened shredded coconut, chopped walnuts or pecans (if using), and dark chocolate chips.
Take a small piece of the dough and flatten it into a small disk in the palm of your hand.
Place a spoonful of the filling in the center of the disk.
Fold the dough around the filling to form a small oval or round shape, pinching the edges to seal.
Heat vegetable oil in a frying pan over medium heat.
Fry the rellenitos in batches, turning occasionally, until they are golden brown and crispy on all sides, about 3-4 minutes per batch.
Remove from the oil and drain on paper towels.
Allow the rellenitos to cool slightly before serving.
Enjoy warm or at room temperature.
Enjoy your meal!