Peel and dice peaches. Place them in a small bowl and mix with cornstarch and cinnamon. Set aside until ready to use.
Slightly warm the milk, then add the sugar and yeast. Stir and let set about 5 minutes until the yeast starts to bubble. Then add in the egg yolk and melted butter. Set aside the egg white for later.
In a large bowl, mix together the flour and salt.
Add the milk and yeast mixture to the flour and stir well. I use a very large bowl and use my hands to finish mixing the dough and knead it for about 3 - 4 mintues. Lift the dough out of the bowl and spray the bowl with non stick spray, put the dough back in the bowl and slightly spray the top of the dough. Cover with plastic wrap and let the dough double in size.
While the dough is rising mix together the cinnamon and sugars for the filling.
When the dough is ready, punch it down and roll it out onto a floured surface. Spread the softened butter over the dough, sprinkle with cinnamon sugar mixture, and top with peaches. Roll up the dough and cut straight down the middle leaving about 2 inches on the top. Pick up one section and lay over the other, repeating until you reach the end. Form the dough into a circle and squeeze together the dough to form a solid circle. Gently place the cinnamon twist in a well oiled baking dish or cast iron skillet.
Let the Peach Cinnamon Twist raise for about 20 - 30 minutes. Brush the twist with the reserved egg white and sprinkle with a little bit of sugar if desired. Bake in a 375 degree oven for 25 - 30 minutes or until golden brown. Let cool and serve.