Halve the avocado, remove the pit, and dice the flesh. Peel the mango, carefully slice the flesh off the seed, and then dice half. Chop just half the cilantro. In a medium bowl, combine the chopped cilantro, diced avocado, diced mango, and juice from half the lime. Add a pinch of salt and stir the mango avocado salsa to combine.
Peel the garlic. Halve the jalapeno and remove the seeds. To a blender, add the remaining mango, cilantro, lime juice, 1 garlic clove, half of the jalapeño, 1 tbsp olive oil, and 1 tbsp water. Blend cilantro sauce until smooth, taste, and season with salt.
Mince the remaining garlic and jalapeño. Drain and rinse the black beans. Place a large nonstick skillet over medium heat with 2 tsp olive oil. Add the minced garlic, minced jalapeño, and cumin, and cook until fragrant, about 1 minute. Add the black beans and a pinch of salt and mash with the back of a fork. Add ½ cup water and cook until beans have thickened, about 2 to 3 minutes. Transfer the black beans to a bowl.
Rinse and dry the skillet and return to medium-high heat with 1 tbsp olive oil. Add 3 tortillas to the skillet in a single layer. Spoon 2 tbsp black beans onto one side of each tortilla and fold in half. Cook until crispy, about 1 minute per side. Repeat with the remaining tortillas. Sprinkle crispy tacos with chili powder and salt.
In a medium bowl, toss the red cabbage with just half of the cilantro sauce and a pinch of salt.
Fill black bean tacos with dressed red cabbage, mango avocado salsa, and dollop with sour cream. Olé!