Put a steamer basket in a pot, and fill the pot with water until it comes up to an inch below the steamer basket.
Add the sweet potatoes, and heat the water on high until it starts to boil.
When the water starts boiling, cover the pot and lower the heat to medium.
Continue steaming the sweet potatoes until they’re soft (test periodically with a fork or a knife). It usually takes me about 30-40 minutes.
Meanwhile, empty the can of black beans into a strainer and rinse with water. Transfer the beans to a sauce pan and add 1 tbsp water. Heat on high and bring the tiny bit of water to a boil. Lower to a simmer, cover, and steam for 5 minutes or until the water has evaporated.
Put the sweet potatoes in a pot and mash them (I like to use a big wooden spoon). Add the black beans and stir. Add the vegan butter, lime juice, and sea salt, and continue to stir until everything is evenly interspersed.