Step 1: Activate Yeast: In a small bowl, combine warm milk, 1 tablespoon granulated sugar, and yeast. Stir gently and let sit for 5-10 minutes until foamy. This confirms your yeast is active.
Step 2: Mix Wet Ingredients: In a large mixing bowl (or stand mixer bowl), combine the remaining ¼ cup granulated sugar, melted butter, and salt. Beat in the eggs one at a time, then add the foamy yeast mixture.
Step 3: Form Dough: Gradually add 4 ½ cups of flour, mixing until a shaggy dough forms. Knead with a dough hook on medium-low speed for 5-7 minutes, or by hand for 8-10 minutes, until smooth and elastic. Add more flour if necessary, but keep the dough slightly sticky.
Step 4: First Rise: Lightly grease a clean bowl. Place the dough in the bowl, turning to coat. Cover with plastic wrap and let rise in a warm place for 1-1.5 hours, or until doubled in size.
Step 5: Prepare Filling: While dough rises, combine softened butter, brown sugar, cinnamon, and 2 tablespoons cooled espresso in a medium bowl. Mix until well combined and spreadable.
Step 6: Roll Dough: Once dough has risen, punch it down. On a lightly floured surface, roll the dough into an 18x12 inch (45x30 cm) rectangle.
Step 7: Spread Filling: Evenly spread the coffee-cinnamon filling over the dough, leaving a ½ inch border on one long edge.
Step 8: Roll and Cut: Starting from the long edge opposite the clean border, tightly roll the dough into a log. Pinch the seam to seal. Using a sharp knife or dental floss, cut into 12 equal 1.5-inch slices.
Step 9: Second Rise: Place the rolls in a lightly greased 9x13 inch baking dish, leaving a small space between them. Cover and let rise in a warm place for 30-45 minutes, or until puffy.
Step 10: Bake Rolls: Preheat oven to 375°F (190°C). Bake for 20-25 minutes, until golden brown. If browning too quickly, tent loosely with foil.
Step 11: Prepare Coffee Soak: While rolls bake, combine ¼ cup warm espresso and 1 tablespoon granulated sugar (if using) in a small bowl. Stir until sugar dissolves.
Step 12: Soak Rolls: As soon as rolls come out of the oven, brush or spoon the warm coffee soak evenly over them. Let absorb for 5-10 minutes.
Step 13: Make Frosting: In a medium bowl, beat softened mascarpone cheese, softened butter, and vanilla extract until smooth. Gradually add powdered sugar, beating until light and fluffy. Add milk/cream if needed for desired consistency.
Step 14: Frost and Serve: Spread the mascarpone frosting generously over the warm (but not hot) rolls. Dust with cocoa powder, if desired. Serve warm and enjoy your decadent Tiramisu Cinnamon Rolls!