Combine the flour and boiling water in a bowl and mix it using a spoon until a dough forms. Wrap this in plastic and refrigerate overnight.
Make the Bread Dough
Sprinkle the yeast over the warm water and let sit for 5 minutes. In the bowl of a stand mixer, combine flour, sugar, salt and milk powder. Whisk to incorporate. Add the yeast mixture, followed by the egg and beat using the dough hook until a shaggy dough forms.
Add the overnight dough and continue to beat until it is incorporated. Add the softened butter bit by bit. Once all the butter has been incorporated, continue beating for about 8-10 minutes. The dough is ready when it can stretch thinly when you pull it apart with your fingers. Take a small portion of dough, use your fingers to pull and spread it wide. A thin, translucent film should form in the center.
Gather the dough into a ball and place it in a greased bowl. Cover it with kitchen towel and set it aside to let it rise for an hour, when it has doubled in size.
Gently deflate the dough and divide it into two equal portions. Divide the first portion into 3 equal portions and roll each portion into a log of about 18-20 inches long. Braid the logs and form a circle by connecting and sealing the two ends. Repeat the same procedure with the other half of dough. Place both braids in a large baking sheet that is lined with parchment paper.
Let the assembled dough rise for another hour. Preheat oven to 350 F. Brush the dough with egg wash, top with grated cheddar cheese and sprinkle sugar over the cheese. Bake in the baking sheet at 350 F for 17-20 minutes.