Heat the milk to 115°F (46°C) and pour it into a large mixing bowl. Stir in the yeast and 1 teaspoon of sugar. Let sit for 5-10 minutes until it turns frothy.

Mix the mashed bananas, egg, yolk, sugar, and 3 cups of flour into the yeast mixture until combined. Add the salt and mix until smooth.

Gradually incorporate softened butter, one tablespoon at a time, until fully blended. Switch to a dough hook and knead, adding more flour as needed, until dough is soft yet tacky and elastic.

Place the dough in a greased bowl, cover, and let it rise in a warm spot for 1-2 hours, or until doubled in size.

Combine brown sugar, cinnamon, cardamom (if using), and salt in a small bowl. Ensure the butter is soft enough for spreading. Preheat oven to 350°F (175°C).

Roll the dough into a 20x8-inch rectangle. Spread the softened butter evenly across the surface, leaving a 1/2-inch border. Sprinkle the filling evenly and add optional diced banana if desired.

Starting from a long edge, tightly roll the dough into a log. Pinch the seam to seal. Use a sharp knife to cut into 12 equal pieces and place them in a greased baking dish.

Cover and let rolls rise again for about 30 minutes until they look puffy.

Bake rolls for 27-30 minutes or until light golden brown. The internal temperature should read 180°F (82°C).

While rolls cool slightly, whisk cream cheese, butter, powdered sugar, vanilla, and milk until smooth. Spread generously over warm rolls before serving.