For the yeast dumplings, dissolve the yeast in lukewarm milk, add 4 tablespoons of flour, granulated sugar and a pinch of salt and mix well.
Dust with a little flour and let rise in a warm place, covered, until doubled in volume.
Add melted butter, the remaining flour, egg and egg yolk and mix until smooth. Cover and let rise for another 30-40 minutes.
On a floured work surface, fold the dough and let rest for 5 minutes and shape into dumplings.
Place on a floured board and let rise, covered, for another 30 minutes.
Bring salted water to a boil in a very large, roomy pot and drop in the dumplings.
Bring to a vigorous boil once and then let steep for 15 minutes with the lid tightly closed.
After about 10 minutes, turn the yeast dumplings over and cook covered for another 4-5 minutes until done.
Lift out and immediately pierce a few times with a thick needle or toothpick to prevent the dumplings from collapsing.
Then tear apart with 2 forks, baste with warm brown butter and sprinkle the yeast dumplings with breadcrumbs.