The elegant Viennese napkin bread dumpling: seasoned bread dough rolled into a cylinder inside a cloth napkin or clingfilm, gently poached in water, and sliced with a thread into tender rounds.
In a bowl, cream the softened butter with egg yolks, salt, and nutmeg. Add the sautéed onions, parsley, warm milk, and bread cubes, tossing gently to moisten the bread without breaking the cubes.
In a clean bowl, whip the egg whites to stiff peaks. Gently fold the whipped egg whites into the bread mixture in two additions; this ensures a light, fluffy, soufflé-like dumpling texture.
Shape the mixture on a buttered cloth napkin or clingfilm into a compact log about 6cm in diameter. Roll up tightly, tying the ends securely with kitchen string while leaving a little slack for the dumpling to swell.
Submerge the wrapped roll in a large oval pot of gently simmering water for 30 minutes. Remove, unwrap, and slice into 1.5cm thick rounds using sewing thread or a very sharp wet knife. Brush with melted butter and serve.