Place the olive oil in a heavy bottomed skillet over medium-high heat. Add the potatoes and a generous pinch of kosher salt, toss well to coat. Cover the skillet with a tight fitting lid and cook for 7-9 minutes, tossing or flipping occasionally to ensure that all sides of the potatoes are browning and getting crisp.
Add the onions and Swiss chard stems to the skillet and cook for an additional 2-3 minutes until softened. Add the black beans to the skillet and mix well; gently arrange into a single layer in the pan. Leave to cook for 2-3 minutes, flipping once or twice, to ensure that the beans are heated through and getting crisp.
Add the ribbons of Swiss chard and cook briefly until it wilts slightly. Remove from the heat and sprinkle in the spices, black pepper, and additional salt to taste. Serve immediately