In a saucepan, scald the milk, stir in the shortening to dissolve. Cool the milk mixture to lukewarm. Pour the warm water into a warm mixing bowl of stand mixer or large bowl. Sprinkle in the yeast and stir to dissolve. Let sit 5 minutes.
In the bowl of a stand mixer, using a dough hook, add the lukewarm milk mixture, sugar, eggs and raisins. Stir in the flour, potato flakes and salt. This dough will be sticky! Use a rubber spatula to scrape the bottom and sides of the bowl occasionally. Knead the dough in the stand mixer for 5-7 minutes.
Turn the sticky dough out onto a very lightly floured work surface. Use a bench scraper to turn the dough into itself, forming into a smooth ball. Be careful not to add too much flour, or it will be dense and tough. This will be a SOFT and sticky dough.
Spray the mixing bowl well with cooking spray or coat with vegetable oil using a clean dry paper towel. Place the dough smooth side up into the warm bowl and cover with plastic wrap. Spray the top of the bread with cooking spray (so the plastic wrap doesn't stick to the bread). Cover with plastic wrap or disposable plastic shower cap and let rise until doubled in a warm place. (About 1-1 ½ hours)
Punch down dough and shape into a round, place back into the greased bowl, cover and let rise another 1- 1 ½ hours, or until doubled.
On a lightly floured work surface, divide the dough into half. Shape into loaves; Roll out into a rectangle shape, brush with butter, spread with cinnamon sugar mixture (keeping it away from the edges of the dough) and roll into a loaf by rolling it into an oblong shape, then tucking and pinching the ends under the loaf. Place the shaped loaves into greased (9x5-inch) loaf pans. Cover with either plastic wrap, disposable plastic shower caps or a clean dry kitchen cloth. Let rise in a warm place until doubled. (30 minutes to 1 hour)
Before placing into the oven, brush each loaf with an egg wash.
Bake in a preheated 375-degree F oven for about 40-45 minutes, until the outside is golden brown and internal temperature is 195-200 degrees. (Place a sheet pan on the bottom rack to catch any butter or cinnamon that might drip out, keeping your oven clean.)
Let the bread cool about 10 minutes before removing from the bread pans. Remove from baking pans and let cool completely on a baking rack.
Let loaves cool completely before slicing.