For the dough
1 cup buttermilk (warmed to 100F)
2 1/4 tsp (7g) instant yeast
1/2 cup granulated sugar
2 eggs
1 tsp kosher salt
4 -4 1/2 cups (520g -585 g) all purpose flour
6 tablespoons room temp butter
For the filling
1 cup brown sugar
2 tbsp cinnamon
1 tbsp cardamom
1 tsp salt
1/2 cup softened butter
For the cream cheese icing
4 oz softened cream cheese
2 tbsp softened butter
1/4 tsp salt
1/2 tsp vanilla
1 cup icing sugar
Let the instant yeast bloom in the warm buttermilk until it foams (about 10 minutes)
In the bowl of a stand mixer fitted with the hook attachment, mix the buttermilk, eggs, sugar, and salt.
Gradually add the flour and mix on medium until a shaggy dough forms. Continue to mix on medium high until a smooth dough forms
While the mixer is going, add butter 1 tablespoon at a time until each piece is fully incorporated. Once all the butter is incorporated continue to knead for 5 more minutes.
Dough should be smooth, shiny and tacky but should not stick to your hands. Add a few more tablespoons of flour if it is too sticky
Transfer dough to a large greased bowl and cover with plastic. Let rise for 90 minutes, or until double in size.
Roll out the dough into a 1/4 inch thick rectangle (about 24 inches x 12 inches)
Mix the brown sugar, cinnamon, cardamom and salt together.
Spread the softened butter on the surface of the dough, then sprinkle to sugar mixture over top. (You can also melt the butter and mix with sugar mixture and spread)
Gently roll the dough by the longer edge and the cut into 10 equal portions (trimming the edges if necessary)
Place in 10inch or 12 inch cast iron pan. Cover with a dish cloth and let rise for 1 hour, or until they have doubled in size.
Preheat oven to 350F. Bake for 20-25 minutes or until golden brown.
While buns are in the oven, make the cream cheese icing by beating the butter with the cream cheese in a stand mixer fitted with the paddle attachment. Add the vanilla, salt and icing sugar and beat until smooth.
Let buns rest about 5 minutes, then spread cream cheese icing over top