Use a grater or food processor with the appropriate attachment to grate the potatoes and carrots. Working in batches, wrap in a clean tea towel and squeeze out as much liquid as possible.
Place in a bowl and stir in the onion, flour, smoked Cheddar, paprika and cumin. Season generously with salt and black pepper, then divide and shape into four small pancakes.
Heat a knob of butter in a frying pan over a medium-high heat. Working in batches if necessary, to avoid crowding the pan, cook the pancakes until golden brown on both sides, adding more butter as needed.
Serve warm, sprinkled with the chopped scallions and salad.