To make the dough: Combine the yeast and sugar in a medium bowl.
Whisk in the milk, egg yolk, and butter. Allow the mixture to rest for 5 minutes; it should foam and froth.
Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess. Whisk together the flour and salt in a large bowl.
Add the milk mixture, and mix and knead until the dough pulls away from the edges of the bowl.
Continue to knead; by hand or mixer until the dough is smooth and soft, though not too sticky. Shape the dough into a ball, place it in a lightly greased bowl, cover it, and let it rest/rise for 30 minutes to an hour. While the dough is resting, make the filling.
To make the filling: Mix together the butter, sugar, and cinnamon.
To assemble the bread: Grease a 10" monkey bread pan or tube pan.
Gently deflate the dough, then place it on a lightly greased surface and roll it into a rectangle about 18"× 12".
Spread the filling evenly on top, leaving a clean 1" border around the edges. Top with the berries.
Starting with a long edge, roll the dough into a fairly tight log; it'll be a bit lumpy because of the berries. Some of the berries will spill out; that's OK, simply set them aside to sprinkle on top once the loaf is in the pan.
Cut the log in half lengthwise, leaving 1" of one end uncut. Starting at the uncut end, twist the two pieces together to form a log, pressing the ends of the two pieces together to seal. Shape the log into a ring, pressing the ends together to seal.
Transfer the loaf to the pan, cover, and let it rise for 45 minutes, until it's puffy. While the loaf is rising, preheat the oven to 375°F.
Brush the loaf with the beaten egg. Bake it for 25 to 35 minutes, until it's golden brown and bubbling.
Remove the loaf from the oven, and after about 10 minutes carefully transfer it to a rack. Cool it for about 30 minutes before serving.