In a medium skillet, heat a tablespoon of oil over medium heat. Add one diced onion and sauté for about 5 minutes until golden brown. Then, add 2 minced garlic cloves and a chopped chipotle pepper, and cook for another minute until fragrant.

Introduce one can of drained and rinsed black beans and half a cup of vegetable stock into the skillet. Lightly mash the beans with a potato masher, leaving some whole for texture. Let simmer for 5 minutes, stirring occasionally, then squeeze in lime juice.

Wrap corn tortillas in a damp paper towel and heat in the microwave for 30 seconds to soften them.

On a lined baking sheet, coat lightly with oil. Spread the black bean mixture on one half of each warmed tortilla, sprinkle with cheese, then fold over.

Preheat the oven to 400°F (200°C) and bake the tacos for 15 minutes, flipping halfway for even browning.

After baking, let the tacos cool for about 5 minutes to enhance crispiness before serving.