Jumbo Cinnamon Rolls

Proof the yeast for the dough in warm water in the bowl of a stand mixer for 5 minutes, or until foamy. Warm the milk to 100 degrees in a saucepan over low heat while the yeast is proofing. Add warmed milk, buttermilk, 3 T. sugar, 2 T. butter, 3 1/2 cups flour, and salt to the proofed yeast. With a paddle attachment, mix on low speed until combined, then increase speed to high; beat for 2 more minutes. Switch to the dough hook and add the remaining 1 1/2 c flour. Mix on low speed until incorporated, then increase speed to medium. Mix for 5-7 minutes, or until dough pulls away from the sides of the bowl. Cover bowl with plastic and let dough rise in a warm place for 1-1 1/2 hours, or until it doubles in size. Butter two 9" square pans. Soften 3/4 cup butter for the filling in a bowl in a microwave for 30 seconds. Use a hand mixer to blend in the sugar and cinnamon; set aside (do not chill). Once the dough has risen, hook your fingers under the edges to release the dough from the bowl. Scrape it onto a well-floured surface, sprinkle with flour over the top, and press gently to remove air bubbles. Divide the dough in half and roll one portion into a 10 x 16" rectangle. Spread half of the filling onto the dough, leaving a 1/2" border. Starting at the shortest edge, roll the dough jelly roll-style into a log. Repeat rolling and filling with the second piece of dough. Transfer logs to a baking sheet and freeze for 10 minutes. Slice each log into 6 rolls and arrange them in the prepared pans; cover rolls with a towel and let rise for 1 hour. Preheat oven to 350 degrees. Uncover rolls and bake for 25-30 minutes, or until browned. Cool rolls in the pans for 10 minutes, then remove and frost with Cream Cheese Icing. Icing: Beat all ingredients together with a hand mixer until combined. Top warm rolls generously with icing after they have cooled slightly.