Boil potatoes in their skins in salted water for about 10 to 15 minutes or until fork-tender (larger potatoes will take longer). Allow to cool until they can be handled easily.
Remove the skins and place potatoes in a medium-sized bowl. Use a potato masher to mash the potatoes until they are of a smooth consistency.
Transfer the mashed potatoes onto a large board. (Make sure they are cool enough, so they won’t immediately cook the egg.)
Add 1 to 1½ cups of flour to the potatoes. Make a well on the center of the flour and add 1 to 1½ teaspoons salt.
Add the egg to the flour well and mix into the potato and flour.
When all of the flour has been fully incorporated into the potato mixture, add the remaining flour. Mix until all of the flour is absorbed and you get the texture of bread dough.
Take a small portion of the dough and roll it into a long log. Using a knife, cut the log into ½-inch pieces. To make the classic gnocchi shape, take a piece of gnocchi and roll it across a fork to leave the impression of the fork tines in the dough.
Cook the gnocchi by boiling it in a large pot of salted water for about 2 to 3 minutes or until the gnocchi floats.
Butter and Parmesan ToppingIn a bowl, place about 2 cups of cooked gnocchi and add 1-1/2 tablespoons of butter, 2 teaspoons of parmesan cheese and mix together well.This recipe makes quite a bit of gnocchi, you can leave the gnocchi until and in an airtight container for up to 48 hours so you can cook it during the next day or two. You can also cook the gnocchi and re-heat it later. I think it is best to cook the gnocchi just before serving.