Activate the Yeast: In a bowl, add warm milk (make sure it's between 100-110°F), 1 tablespoon of sugar, and yeast. Mix briefly and let sit until foamy, about 5 minutes.

Make the Dough: Add the eggs, softened butter, remaining sugar, both flours, and salt to the activated yeast. Mix with a dough hook on low speed until combined, then increase to medium speed and knead until smooth (about 5 minutes).

First Rise: Place the dough in a greased bowl, cover it with a damp cloth or plastic wrap, and let rise until doubled in size, about 1-2 hours.

Prepare the Filling: While the dough is rising, combine softened butter, brown sugar, granulated sugar, flour, vanilla extract, and salt in a small bowl. Mix until smooth and set aside.

Roll It Out: Once the dough has doubled, roll it out onto a lightly floured surface into a rectangle approximately 1/4-inch thick. Spread the filling evenly over the dough, and sparsely sprinkle rainbow sprinkles on top.

Shape the Rolls: Starting from the long edge, tightly roll the dough into a log. Cut the log into 9 equal rolls and place in a greased baking dish.

Second Rise: Cover the rolls and let them rise again until doubled in size, about 1 hour. Preheat the oven to 325°F.

Bake: Once risen, bake the rolls for 35-40 minutes until golden brown.

Make the Frosting: While the rolls are baking, prepare the frosting by mixing cream cheese, softened butter, confectioners' sugar, vanilla extract, and a pinch of salt until smooth.

Frost and Garnish: As soon as the rolls come out of the oven, spread frosting over the warm rolls and top with additional rainbow sprinkles.