Step 1: In a large bowl, combine the warm milk, yeast, and 1 tablespoon of granulated sugar. Stir gently and let it sit for 5-10 minutes, or until foamy. This indicates the yeast is active.
Step 2: Add the remaining granulated sugar, melted butter, eggs, vanilla extract, salt, and mashed bananas to the yeast mixture. Mix well.
Step 3: Gradually add 4 cups of flour, mixing until a shaggy dough forms. Turn the dough out onto a lightly floured surface and knead for 5-7 minutes, adding more flour a tablespoon at a time if the dough is too sticky, until it's smooth and elastic. It should still be slightly tacky.
Step 4: Lightly grease a large bowl with oil. Place the dough in the bowl, turning once to coat. Cover with plastic wrap or a clean kitchen towel and let rise in a warm, draft-free place for 1-1.5 hours, or until doubled in size.
Step 5: While the dough is rising, prepare the filling: In a small bowl, cream together the softened butter, brown sugar, and cinnamon until well combined.
Step 6: Once the dough has doubled, punch it down gently to release the air. Turn it out onto a lightly floured surface and roll it into a large rectangle, approximately 12x18 inches.
Step 7: Spread the cinnamon filling evenly over the entire surface of the dough, leaving a small border (about ½ inch) on one long edge.
Step 8: Starting from the long edge opposite the border, tightly roll the dough into a log. Pinch the seam to seal.
Step 9: Using a sharp knife or unflavored dental floss, cut the log into 12 equal slices (about 1.5 inches thick).
Step 10: Arrange the rolls in a lightly greased 9x13 inch baking pan, leaving a little space between each roll. Cover the pan with plastic wrap or a kitchen towel and let them rise again in a warm spot for 30-45 minutes, or until noticeably puffy.
Step 11: Preheat your oven to 375°F (190°C). Bake the rolls for 20-25 minutes, or until golden brown and cooked through. If they start browning too quickly, you can loosely tent them with foil.
Step 12: While the rolls are baking, prepare the cream cheese frosting: In a medium bowl, beat the softened cream cheese and butter with an electric mixer until smooth and creamy. Gradually add the sifted powdered sugar, vanilla extract, and 1 tablespoon of milk (or cream). Beat until light and fluffy, adding more milk if needed to reach your desired consistency.
Step 13: Once the rolls are out of the oven, let them cool in the pan for 5-10 minutes. Then, spread the cream cheese frosting generously over the warm rolls. Serve immediately and enjoy!