To prepare the dough

1. In the bowl of a stand mixer, stir together the warm milk and 2 teaspoons of sugar. Evenly sprinkle the yeast over top of the milk and allow the yeast to activate, about 5 minutes. The mixture should froth and foam slightly. You can stir it gently to make sure all the yeast has been moistened, but if the yeast does not foam, dump it out and start over. Once yeast has been activated, beat 1/2 cup of the flour in to the milk mixture using the paddle attachment. Once combined, add the remaining sugar, eggs, egg yolk, vanilla, and salt, and beat the mixture on medium speed until combined. On low speed, add the remainder of the flour, 1/2 cup at a time, scraping the sides of the bowl as needed. Once evenly combined, increase the speed to medium (I use speed number 4 on my Kitchen Aid stand mixer) and add the softened butter 1 tablespoon at a time. Scrape the sides of the bowl and then continue to beat on medium speed for an additional 4 minutes. The dough will be quite moist and sticky, and will hold together in long strands when you attempt to scoop it from the bowl.
2. Lightly grease a large bowl and place the dough inside, covering it tightly with a piece of plastic wrap. Allow the dough to rest until it has approximately doubled in size, about 1-1/2-2 hours. Once the dough has nearly doubled in size, prepare the filling.

To prepare the filling

1. Combine the cooled, melted butter, sugars, cinnamon, flour, and salt, stirring until combined. Add the egg white, stirring just until combined. You will use approximately ½ cup of filling for each loaf.

To prepare the loaves

1. Once the dough has doubled in size, line 2 loaf pans (8 1/2″ x 4 1/2″ x 2 3/4″) with parchment paper. Cut two sheets of parchment paper- one to fit the pan lengthwise and one to fit widthwise- with some extra paper to hang over the sides.
2. Generously flour your work surface and rolling pin. Prepare your egg wash by whisking together the egg and water. Set aside.
3. Gently punch the dough down into the bowl once and divide the dough in half. Take one half of the dough and lay it on your floured surface. Generously dust the top of the dough with flour as well. Using your rolling pin, roll your first piece of dough as evenly as possible into a 22″x10″ rectangle. (I even use a ruler!) You may need to re-flour your work surface if the dough begins to stick. Using a pastry brush, lightly paint the outside 1/2″ edges of your dough with your egg wash. Spread half of the filling (about ½ cup) evenly inside the egg wash border.
4. Standing with one of the long edges closest to you, begin to tightly roll your dough away from you, forming a 22″ long roll of dough. Gently pinch the dough together at the seam to seal the filling inside the roll.
5. Spread about 1-2 tablespoons of filling on the top of the roll of dough and then fold it on top of itself, forming an 11” long folded roll of dough. Shape the loaf, by pulling the ends of the dough roll together to form a “U” shape. Twist the two ends over each other twice to form a figure 8 shape and tuck the end pieces under the dough. Place your rolled loaf in one of the prepared pans and repeat the entire process with the remaining half of dough. Once both loaves have been formed, cover again with plastic wrap and allow to rise again for about 1-1/2-2 hours. The dough should rise about 1/2-1″ over the top of the pans. Do not let them over-rise.
6. When the dough is nearly risen, preheat the oven to 350 degrees and brush the remaining egg wash over the tops of the loaves. Bake in the preheated oven for about 40 minutes, or until the tops are a dark golden brown and no longer squishy or underbaked looking. Look especially for underbaked parts in the creases of the twists on top of the loaves. Allow to cool in the pans on a cooling rack for about 20 minutes and then remove from the pan to cool completely.