To make the avocado dressing, blend all the ingredients in a jug with a hand-held blender until smooth. Season with black pepper and set aside.
Heat a large non-stick frying pan over low–medium heat. Combine the sweet potato, haloumi and cumin in a bowl and season with freshly ground black pepper. Lightly spray the pan with olive oil and drop in firmly packed ½ cup measures of the sweet potato mixture, pressing down to form 8cm circles. Depending on the size of your pan, you will probably need to do this in two batches of four. Cook for 5 minutes each side or until golden and cooked through. Remove and cover to keep warm.
Lightly spray the pan with a little more oil and increase the heat to high. Add the garlic, white part of the spring onion, spinach and ¼ cup (60ml) water. Cook, tossing constantly, for 2 minutes or until the spinach has just wilted. Remove the pan from the heat and season with black pepper.
Serve two sweet potato fritters per person, layered with the spinach mixture. Spoon over the dressing and sprinkle with the green spring onion.