Dough: Mix the flour, yeast, sugar, and salt. Add the water and the egg. Knead the dough in the food processor or with a hand-held mixer with kneading attachments until the dough is smooth and doesn't stick anymore, about 5 minutes. Add a little more flour if the dough is too sticky or a bit of water if the dough is too tough. Knead the dough briefly on the working surface, place it in a bowl, cover with a clean kitchen towel. Let rise in a warm place for about half an hour or until double in size.
Butter a loaf pan (about 23 cm/ 9 inches) if you use a normal one. You don't need to butter it if using a silicon mold.
Halve the plums and slice the halves very thinly. Mix 50 g soft butter with 2 tablespoons of the brown sugar. Knead the dough shortly on the working surface. Divide the dough into equal-sized balls, about as large as a golf ball. I had 14 of them.
Roll each ball into an oval slice (you can lightly flour the working surface if you find it necessary, I didn't need to). Spread a little of the butter-sugar mixture on each slice, place a few plum slices on top and sprinkle with some cinnamon. Spread some butter-sugar mixture on the last one as well, but do not add plums anymore.
Assemble: Stack about 3 slices of dough over each other, leaving the one without the plums aside. When all of them are stacked into small groups, take one group at a time and place it in the buttered loaf pan, the way you would put books in a bookshelf. Close the row with the plum-free slice; the buttered side should face the previous piece.
Let rise: Cover the pan with the kitchen towel and let rise again for about 20-30 minutes, until visibly risen.
Preheat: While the bread rises, preheat the oven to 180 degrees Celsius/ 350 degrees Fahrenheit.
Top: When the bread has risen, melt the remaining butter and pour evenly on the bread. Sprinkle with the extra tablespoon of brown sugar and with some more cinnamon.
Bake for about 25 to 30 minutes until the bread is cooked through but still soft. It should be nicely browned as well. Check the bread after half of the baking time; if it gets dark too soon, cover lightly with aluminum foil.