For the sponge
1/3 C. whole milk
2 tsp. instant yeast
1 tsp, sugar
1 1/2 tsp. Kosher salt
1/2 C. all-purpose flour, divided
For the brioche dough:
2 1/2 C. bread flour
3 T. sugar
5 large eggs
1 C. butter at room temperature
For the filling:
1/2 C. butter room temperature
2/3 C. granulated sugar
1/3 C. packed brown sugar
1 1/2 T. cinnamon
1/2 tsp. salt
For the glaze
2 C. powdered sugar
1/2 C. milk
Scald milk. Cool to 100°. Pour into bowl of stand mixer, add sugar, salt, instant yeast and 1/4 C. cup of flour. Mix on low speed until combined. Sprinkle remaining 1/4 C. flour on top. Set aside to proof for 30 minutes.
When the sponge is ready, add dough hook, turn on low, add 2 to 2 1/2 C. bread flour, 3 T. sugar and eggs one at a time. Mix on medium until the mixture is smooth and add all flour is incorporated.
Add butter in 1/3 C. increments until it’s all incorporated. Turn mixer up to medium high and mix 3 minutes.
Transfer to oiled bowl, chill in refrigerator 12 hours or overnight.
On a well-floured surface, roll the dough into a rectangle about 18 X 24 inches and 1/4 inch thick.
Spread the butter evenly across the top of the dough. In small bowl, combine the brown and granulated sugars, cinnamon and salt. Spread evenly across the buttered dough. Roll the dough the long way. Cut into 1-inch rolls, lay on the side into a well buttered pan. Allow to proof at room temperature until the dough lightly springs back when touched.
When ready, bake at 350° until slightly browned on top or to the internal temperature of 190°. While allowing rolls to cool, mix glaze and drizzle on top of rolls.