Dissolve yeast in 100 ml of warm milk (max. 37 ° C). Put 400 g flour in a large mixing bowl. Add sugar, cinnamon, egg, salt, softened butter and the remaining 200 ml milk. Process all ingredients into a dough and cover and let rise in a warm place (approx. 28 ° C) for 45 minutes. If the amount of dough has doubled, it is exactly right.
Knead the dough vigorously again with the remaining 50 g flour. It should no longer stick and separate from the edge of the bowl. Roll out the yeast dough into a square about 0.5 cm thick on a floured work surface.
Now brush or brush with the soft butter. Mix the sugar with the cinnamon and sprinkle over the butter. Roll the whole thing up into a tight sausage and cut off approx. 1.5 cm thick slices with a sharp knife. Tip: With the help of a thin string or a fishing line, you can also cut thin slices by placing the thread below the sausage, crossing it above and pulling it together. This is how you get a perfect record.
Place the slices on a baking tray lined with baking paper with sufficient space between them, brush with melted butter and sprinkle with sugarcoat. Cover and let rest for another 20-30 minutes.
Set the oven to 250 ° C top / bottom heat (no circulating air, otherwise they will get dry). Put the baking sheet in the oven and set the temperature back to 200 ° C, bake the whole thing for 10 - 15 minutes until the rings are lightly golden brown (use experience from your own oven and check in between times.
The donuts taste particularly delicious when they are nibbled while warm.