Mojo:
Using a mortar and pestle, add garlic, salt, and peppercorn; mash mixture into a paste. Add orange, lime juice and oregano; stir to combine. Add mojo to shredded chicken and let stand at room temperature 30-45 minutes.
Chicken Vaca Frita Tacos:
In a large pan, add 2 tablespoons olive oil and sauté onions. Season with salt and black pepper; cook 4-5 minutes until golden in color. Transfer onions to a platter. In the same pan, heat remaining 3 tablespoons of olive oil. Add shredded chicken and fry one side 4-5 minutes, until brown and crispy. Using a spatula, flip the shredded chicken and continue to crisp the other side. Add onions back to pan and stir to combine with the chicken.
To assemble tacos, top each tortilla with shredded chicken, black beans, and mango salsa. Enjoy!
Mango Sala:
In a serving bowl, combine all ingredients and mix well. For best flavor, let the salsa rest for 10 minutes or longer.