Steam the sweet potato until soft but still firm enough to keep its shape, 5–10 minutes. Drain and rinse under cold water to quickly cool.
Put the chickpeas in a medium bowl and coarsely mash, leaving some beans intact. Add the sweet potato, bell pepper, and raisins and stir to combine.
Put the nutritional yeast, tahini, water, milk, mustard, vinegar, horseradish, ginger, turmer