Combine Wet Ingredients: Add the egg, mashed banana, melted butter, and vanilla extract to the yeast mixture. Whisk until combined.
Add Dry Ingredients: Attach the dough hook to your mixer. Add the 3 cups of flour, 1 tsp cinnamon, and salt. Mix on low speed until the dough comes together.
Knead the Dough: Increase the speed to medium and knead for 5-7 minutes, until the dough is smooth and slightly tacky but pulls away from the sides of the bowl. If the dough is too sticky, add 1-2 tablespoons of flour at a time. (You can also knead by hand on a floured surface for 8-10 minutes).
First Rise: Form the dough into a ball. Place it in a lightly greased bowl, turning it once to coat. Cover the bowl with plastic wrap or a clean kitchen towel and let it rise in a warm, draft-free place for 1-1.5 hours, or until doubled in size.
2. Assemble the Rolls:
Prepare Pan: Grease a 9×9 inch square or a 9-inch round baking pan.
Roll the Dough: Once the dough has risen, punch it down to release the air. Turn it out onto a lightly floured surface. Roll it into a 12×16 inch rectangle.
Spread the Filling: Spread the very soft ½ cup of butter evenly over the entire surface of the dough, leaving a ½-inch border along one of the long edges.
Add Sugar & Spice: In a small bowl, mix the brown sugar, 2 tsp cinnamon, and nutmeg. Sprinkle this mixture evenly over the butter. If using nuts, sprinkle them on top.
