Combine the milk and butter in a microwave-safe bowl and Heat 1 minute. Remove and stir and continue to heat in 15 second increments {sirring in between}, until liquid is warm but NOT hot.
In another bowl, combine 3 cups of the flour with the sugar and salt.
Using a stand mixer with the dough hook attachment, add warm but not hot yeast and milk mixture and stir by hand until combined.
Add the flour mixture as well as the egg, then beat on medium-low speed until combined. You don't want the dough to stick to the sides of the bowl, so add the remaining flour a bit at a time until the dough forms a ball and pulls away from the sides of the bowl. Continue beating for 4 minutes on medium-low speed.
Remove the dough from the hook and cover bowl with a damp towel to rest for 10 minutes.
When the dough is ready, turn it out onto a floured work surface. Using a floured rolling pin, roll the dough out into a rectangle, at least 14 x 9 inches in size. Once it's rolled, use a pizza cutter to shape the dough into a perfect rectangle.
Use a knife or spatula to spread the REESE evenly over the top of the surface. Sprinkle the cinnamon evenly on top.
Beginning at a long edge of the rectangle, roll up the dough. Use dental floss or a sharp knife to cut the two ends of the roll, to make it even. Then cut the remaining dough into equal pieces.
Place each of the cut REESE cinnamon rolls into a greased baking dish or pie plate. Then cover again with a damp towel in a warm place for 45 minute to an hour. I turned on my oven to 250 degrees, with the dish on top of the stove.
While the dough is rising, make the icing by whisking the butter and cream cheese together then adding the icing sugar and 1 tbsp of milk. If the icing is too thick, add the a tad more milk to thin.
When the rolls have risen, uncover the dish and bake at 350 degrees for 14-19 minutes, or the tops start to brown. Remove from the oven and let cool on a wire rack for at least 5 minutes then drizzle with the icing and some softened REESE Spread if desired.