Place the grated potatoes in a cloth and wring as much of the moisture out as possible. Place the potatoes into a bowl, and stir in the onion soup mix, garlic, eggs, flour, Cheddar cheese, salt and pepper until well mixed.
Heat the vegetable oil in a large frypan over medium heat until it shimmers and drop the potato mixture by heaping tablespoons into the hot oil. Press down on the patties to flatten them to about 1cm thick. Fry the patties until golden brown and crisp on the bottoms, 5 to 8 minutes, then flip and cook the other side until crisp and golden. Remove the latkes to paper towels to drain and serve hot, sprinkled with spring onion and a small dollop of sour cream.