For pasta dough, place flour into a large bowl, make a well in the centre and break in eggs, add 1-2 tbsp water and using a fork bring together in a coarse dough. Then turn onto a clean bench and knead until smooth. Cover with a tea towel and set aside to rest for 1 hour.
Preheat oven on steam setting. Spread spinach leaves over a steam tray, then place in the oven and steam for 1 minute or until wilted. Remove and refresh under cold running water. Squeeze spinach to remove excess water and set aside.
Heat half the butter in a large frying pan, add half the onion and cook over low heat until onion is soft, about 10 minutes, add mince and cook until browned, then add parsley and breadcrumbs and stir to combine.
In a bowl, combine spinach, mince mixture, chopped sausage with beaten egg. Season to taste with salt, freshly ground black pepper and grated nutmeg.
Using a pasta roller, roll out pasta dough into sheets 1-2mm thick, then cut into manageable lengths. Spread filling evenly over rolled dough, leaving a 1cm strip down one long side. Brush this side with eggwash, then roll like a strudel beginning at the covered side and finishing at the eggwashed side.
Using the handle of a wooden spoon, press diagonally into rolled pasta every 5cm to form diamond patterns, then cut with a knife into pieces and place onto a lightly greased steam tray. Steam in oven for 20 minutes or until pasta is tender and filling warmed through.
Heat remaining butter, add remaining onion and saute over medium heat until golden brown, about 10 minutes. Spoon over steamed maultaschen and serve immediately, topped with pepper and grated nutmeg.