Mashed Potato Gnocchi

INSTRUCTIONS

1. 1Stir mashed potatoes with egg yolk. Add flour and salt; stir until well combined, adding additional flour, a bit at a time, to make stiff, dry dough.
2. 2On floured surface, knead dough 4 to 5 times until smooth. Divide into 4 portions. Roll each portion into long rope, about 1 cm (1/2-inch) thick. Cut into 2.5 cm (1-inch) pieces. Roll fork over each piece to create pattern.
3. 3In large pot of boiling, salted water, cook gnocchi for about 2 minutes or until gnocchi floats to the surface. Remove with slotted spoon and drain well; toss with warm marinara sauce, butter or olive oil. Sprinkle with Parmesan cheese (if using).