Make a yeast dough from the dough ingredients, leave the pre-dough to rise for 25 minutes and let the finished dough rise for 45 minutes.
In the meantime, cut the bacon into small cubes and allow to translate in a pan and add the finely chopped onions. Let roast for a few minutes. Season to taste with salt, pepper and finely weighed parsley.
Roll out the well-raised yeast dough and cut out slices about 8 cm in diameter (or wheel out appropriately large squares). Cover half of the slices with the filling, brush the edge with whisked egg white. Beat the second half of the slices over the fillings. Press the edges firmly together. Place on a greased baking sheet and let rise again. Then brush with egg yolk, which has been mixed with a little milk.
Bake on the middle rack at approx. 210 degrees for about 25 minutes.