In a small bowl, stir together yeast, warm water and 1/2 teaspoon sugar. Set aside for 5 minutes to "proof". (If the mixture doesn't get foamy on top, either the yeast is bad or the water was too hot). For instant yeast, add yeast, water and sugar with everything in step 2.
In a stand mixer or large bowl add the yeast mixture, warm milk, sugar, melted butter, salt and egg. Add 2 cups of flour and mix until smooth. Add another cup of flour and mix or knead until combined. Continue kneading the dough for about 5 minutes, adding additional flour as or if needed to reach a soft dough that pulls away from the sides and bottom of the bowl and is not overly sticky, but very soft. Be careful not to add too much flour.
Place dough in a well-greased bowl, cover and let rise until doubled in volume, about 1 1/2 hours. Meanwhile, butter a rimmed bakers half sheet (18x13'') or a 9x13'' pan. Set aside.
Dust a work surface lightly with flour, or spray with non-stick cooking spray. Punch down the risen dough and transfer to work surface. Roll it out into about a 20''x18'' rectangle.
Spread the 6 tablespoons of softened butter over the top of the dough. Mix sugar and cinnamon together, and then sprinkle over buttered dough, leaving 1/2 inch border. Sprinkle with walnuts, pecans, or raisins if desired.
Beginning on the 18-inch side, role up dough tightly into a log. Pinch the ends together to seal. Cut into 12 equal portioned pieces (about 1 1/2 inches wide). A sharp serrated knife or a piece of floss work well to cut the dough.
Arrange rolls on prepared baking sheet and cover with plastic wrap (I like to spray the plastic wrap lightly with cooking spray first, so it doesn't stick to the dough). Allow the rolls to rise again for about an hour, until doubled in volume.
Preheat oven to 375 degrees F. Once risen, uncover rolls and bake for 18-22 minutes or until no longer doughy in the center.
While the cinnamon rolls bake, make the icing. Mix butter and powdered sugar together for several minutes. Mix in vanilla, and enough milk to reach a soft frosting consistency.
Spread icing over hot cinnamon rolls, right from the oven.
Yeast: to substitute Instant or rapid rise yeast skip the first step of proofing. Mix the yeast with 2 cups flour, sugar and salt before adding that to the stand mixer with warm water, milk, egg, and butter. Note that the rolls may rise faster when using instant yeast.
Tip for Quick Rise Cinnamon Rolls: Make dough up to first rising, placing it in a well greased bowl, turning it once to grease the dough all over. Cover bowl with plastic wrap. Preheat oven to 180 degrees F, then turn oven off. Place bowl into the oven, leaving the oven door slightly cracked open. Allow to rise until doubled. Then remove, punch down and roll out.
For Cream Cheese Icing: beat 4 ounces softened cream cheese with the butter. Omit the milk, and mix in vanilla and enough powdered sugar to reach a soft frosting consistency, 1 1/2 - 2 cups.Storing Instructions: Once cooled, store leftover cinnamon rolls in an airtight container for up to 2 days at room temperature, or 1 week in the fridge. Rewarm individually in microwave for about 15 seconds or until soft.Make Ahead Instructions: Make dough and assemble rolls through step 7 (just before the second rise). Cover really well with plastic wrap or a lid and let rise in the refrigerator for several hours, or overnight. Remove from fridge, keep covered and allow to rise until doubled in volume, about 1 to 1 1/2 hours, before baking.You could also refrigerate the dough after step 2 and allow it to rise for several hours in the fridge, before rolling out, filling and baking. Freezing Instructions: Baked rolls can be frozen for up to 3 months. Thaw overnight in the refrigerator and warm in the microwave for a few seconds. To freeze unbaked cinnamon rolls, bake the assembled rolls for only about 12 minutes at 375°F. Allow to cool completely, then cover well and freeze. Thaw overnight in the refrigerator, then return to oven for 10-15 minutes, until cooked through.