Drain the soaked beans and transfer to a food processor. Add the parsley or cilantro, salt, shoyu, and cumin. Blend until the beans are chopped to fine shreds, but don’t blend them to a pulp. The mixture will be slightly wet but should hold together. Form the bean mixture into something between football- and UFO-shaped croquettes in the palms of your hands.
Heat 1 inch of oil in a cast-iron skillet to about 180°C/350°F/gas mark 4. To test the oil, drop in a tiny amount of croquette mixture. If it bubbles furiously and rises to the top, the oil is ready. Do not let the oil get so hot that it smokes. You may need to make little adjustments to heat under the oil throughout the cooking process to avoid burning the croquettes.
Place 4 croquettes in the oil and fry for about 4 minutes on each side. Use a slotted spoon to transfer the fried croquettes to a plate lines with paper towels or a paper grocery bag to drain.
To make the dipping sauce, stir together the barley malt syrup and mustard in a small saucepan. Warm the sauce over low heat until it bubbles.
Serve the croquettes while still hot. Drizzle with the dipping sauce or serve it alongside the croquettes in individual dipping bowls.