Place Edgell Instant Mash in a large bowl. Carefully add boiling water and mix with a fork until it resembles mashed potato. Add egg yolk and stir well.
Add plain flour; mix until all the flour is incorporated and the mixture is thick. Sprinkle a little extra plain flour on the bench. Take ½ cup of the potato mixture and roll into a long sausage shape. Cut into 2cm pieces and place onto a floured tray. Continue with remaining mixture.
Bring a large saucepan of water to the boil. Carefully place the gnocchi pieces in the water and cook for 5 minutes or until they float to the surface.
Remove gnocchi with a slotted spoon. Serve with a hot pasta sauce of your choice and sprinkle with a little grated parmesan cheese.