This recipe is from the acouplecooks.com, an awesome blog with tons of unique vegetarian recipes. The only difference I've made was adding corn, which makes this a more healthy vegetarian meal with complete amino acids.
In a medium pot, heat 2 tablespoons olive oil. Add garlic and cook for about 1 to 2 minutes until the garlic is just fragrant barely starting to brown. Add the black beans along with the can liquid, corn, 1 tablespoon of cilantro, 1/2 teaspoon salt and 1/4 teaspoon pepper. Bring to a boil, then simmer 15 minutes or until the liquid condenses.
While the beans & corn cook, prepare the salse: Combine 1 tablespoon olive oil, 3 tablespoons cilantro, 1/2 teaspoon salt, 1/4 teaspoon pepper, radishes, green onions, serrano pepper and lime juice.
To serve the tacos, place the beans & corn in the middle of a tortilla and top with salsa and feta. Sprinkle with additional cilantro, if desired.