In a pan set over low heat, combine your milk, 4 ounces of room temperature butter, and white sugar. Heat until just warm (110°F), then remove, swirling to melt butter. Add in yeast and stir. Let proof 10 minutes.
When yeast is foamy and proofed, beat together the egg and egg yolk. Combine the eggs, yeast/milk mixture, 3 cups (13 ounces) of flour, salt, and vanilla in a large bowl.
Fold together ingredients until a sticky dough forms. Continue to gently work until it becomes a tacky but manageable ball, about 5 minutes. Sprinkle in remaining flour 1 tablespoon at a time if it's too sticky, but only add as much as needed.*
Lightly sprinkle the ball of dough with flour then cover and set in a warm place to rise until doubled. Between 45 minutes to 1 hour.
When dough has risen, combine the remaining 4 ounces of softened butter, 4 ounces of softened cream cheese, brown sugar, and cinnamon in a bowl and beat together until creamy.
Turn out dough onto a clean, lightly floured surface and press into rectangle shape. Lightly flour your rolling pin and roll into a 16x12 rectangle.
Spread your filling gently on the rectangle of dough, leaving only 1/2 inch of dough exposed on either long edge.
Beginning on one long edge, begin to tightly roll the dough into a log, rolling forward with the palm of your hands and working from one end to the other to keep it even.
Once rolled, gently slice into rounds about 1 1/4 inch thick.* Place rounds in a 13x9 baking dish, leaving a small gap between each roll.
Cover loosely and let rise again, 45 minutes to one hour, or until puffy and the gaps between the rolls have filled in.
After 30 minutes, preheat your oven to 350°F. When rolls are risen, place on middle rack and bake for 30 minutes, or until golden brown on top.
While your cinnamon rolls cool, combine the powdered sugar, remaining cream cheese, and vanilla in a bowl and beat until smooth. Add half the milk and beat, adding the remaining milk slowly until icing is at desired consistency and smooth.
Liberally spread icing on the tops of the cinnamon rolls. Serve and enjoy! Cover, and store in the fridge for up to 3 days.
*I ended up using 15 ounces, about 3.5 cups of flour for this. Start with three and add up to the remaining half cup as you mix the dough. *You can use unflavored dental floss or fishing line to slice the cinnamon rolls, or use a very sharp knife with a gentle sweeping motion. Do not press or saw the dough to avoid crushing the shape.*If making these the night before, please see the FAQ section for detailed instructions.