Preheat oven to 200° and place 2 baking sheets in oven.
Using a hand grater, grate onion and transfer grated onion to a colander and set in sink to drain.
Grate the potatoes and transfer them to the colander with the onions and leave to drain for a few minutes.
In a large bowl, whisk together egg, flour, salt, pepper and baking powder.
Using a dish towel or cheese cloth gently squeeze excess liquid from the potatoes and onion.
Add the potato mixture to the large bowl with the egg and flour mixture.
Use your hands to gently combine the ingredients.
Heat 1 T oil and 1 T Butter in a large skillet over medium high heat.
Scoop about ¼ C of potato mixture at a time in the skillet and flatten with spatula (you can get 2 to 4 pancakes in the skillet depending on size).
Turn burner down to medium heat.
Cook until golden brown on both sides (about 3 to 4 minutes on both sides) and remove from skillet and place on paper towels to drain.
Wipe out skillet with a paper towel after each batch and re-oil.
While second batch is cooking, place the cooked draining pancakes on the cooking sheets in the oven.
Repeat until all pancakes are cooked.
Serve warm.
Chef's notes: Good with Pork chops and applesauce. Original recipe credited to Della Garretson Hoover.