Preparation / Directions:
Start heating oven to 350øF. In a large bowl, combine mashed potatoes, flour, egg yolks, 2 tsp salt, pepper, mustard and 10 ozs shredded cheese. Meanwhile, in a large kettle, bring the hot water to a slow boil; add 1 tbs salt. In large pastry bag, with large plain tube #8 in place, put some of potato mixture. Holding bag over simmering water, force contents through tube, snipping it into 3/4" ;pieces of gnocchi with scissors. Cook gnocchi gently until they rise to surface, when they will be done. As gnocchi rise, remove at once with a slotted spoon; drain well on paper towels; place in buttered 1 1/2-qt. shallow casserole; keep warm in oven. Repeat snipping, cooking, draining, and warming remaining dough until all is used up. Remove casserole from oven; turn broiler to Broil; pour butter over gnocchi, and sprinkle with remaining shredded cheese. Broil till golden - about 5 minutes.