Classic Cinnamon Rolls

Lightly grease a large bowl and a 9"-x-13" pan with cooking spray. In a separate large bowl or in the bowl of a stand mixer using a dough hook, mix together milk and yeast until yeast is mostly dissolved. Add in all remaining dough ingredients on low speed. Continue mixing on medium-high speed until a smooth, soft dough forms and starts to pull away from the sides of the bowl, 15 to 18 minutes. Transfer to greased bowl and rotate so that outside of dough is thoroughly greased. Cover with a kitchen towel and let rise until almost doubled, 1 1/2 to 2 hours. Meanwhile, make filling: In a large bowl using a hand mixer, cream together butter, sugar, cinnamon, nutmeg if using, and salt until light and fluffy, 3 to 4 minutes.  Preheat oven to 400°. Turn the dough onto a lightly floured surface and dust with more flour. Roll out into a large square, about 18"-x-18". Spread to edges with filling, then roll the dough into a log and cut into 12 evenly sized pieces, each about 1 1/2" wide.  Place rolls cut side-up in prepared baking pan. Cover and let rise again until almost doubled, 30 to 40 minutes.  Bake until golden, 20 to 22 minutes.  Meanwhile, make frosting: In a large bowl, combine butter and cream cheese and beat until light and fluffy. Add powdered sugar, salt, and vanilla and beat until smooth. Gradually add milk (or heavy cream) to loosen icing.  Remove cinnamon rolls from oven and frost immediately. Serve warm.