Mix the grated potatoes and onions together, then place in the centre of a clean, dry tea-towel or piece of muslin. Gather up the sides around the mixture, and over a bowl (or the sink) squeeze out as much moisture as possible.
Place the dried potatoes and onion into a bowl and stir in the matzoh meal, egg, and salt, then mix together well.
To shallow fry, pour about 1cm/½" oil into a large frying pan over a high heat. To test the heat of the oil, drop a small cube of bread into the pan. It should brown in around 60 seconds.
Make balls of the latke mix (about 2-3 tablespoons) in your hand, making sure they are nice and compact. Place into the frying pan and flatten out with spatula. Do not crowd the pan as the temperature of the oil will drop. Depending on the size of your pan, make 3-5 latkes at a time. The should take around 3-5 minutes to cook each side - or until crisp and golden brown.
When cooking fried food, I find it helps to do a test batch first to make sure that the oil is perfect, and that the latke mixture holds together. If it doesn't, you can always add a little more matzoh meal to your potato mixture.
Once cooked, drain the latkes on paper towels, brown paper, or on a wire rack. Serve immediately with sour cream or apple sauce.