Peel, slice and grate the raw potatoes using a mandolin, or cube the raw potatoes and grate till fine in food processor.
Put the grated potatoes in a clean kitchen towel and squeeze out as much liquid as possible
Peel and grate the onion using a mandolin or food processor
In a large bowl, beat the 2 eggs. Add the grated potatoes and grated onion, mix well. Add the flour and mix with a spatula. If the mixture looks too wet, add more flour. The mixture should feel gluey, not dry.
Heat the frying pan, add oil to completely cover the surface with a thick layer. Heat oil till very hot. Scoop the potatoes mixture (1/3 cup to 1/2 cup depending on your prefered size) in the hot oil and use a spatula to flatten the potatoe mixture. Fry the pancakes till golden on both sides (about 3 to 5 minutes per side). Depending on your frying pan size, you can fry by batch of 2 to 3 potato pancakes at a time.
Drain the pancakes on paper kitchen towel and keep warm, till you finish frying all the pancakes. Serve hot with a side of apple sauce and sour cream.