Adapted from cooks.com
Makes two pans of 12 rolls
2 packages yeast
1/2 c. warm (not hot) water
2 c. lukewarm milk
1/2 c. granulated sugar
3 tsp. baking powder
1/3 c. soft butter (plus extra for kneading)
2 tsp. salt
1 egg
5-6 c. all-purpose flour
Filling
4 Tbsp. soft butter
1/2 c. granulated sugar
1/4 c. brown sugar
1 Tbsp. + 1 tsp. cinnamon
Icing
6 Tbsp. butter
3 c. powdered sugar
1 1/2 tsp. vanilla extract
3-6 Tbsp. hot water
In the mixing bowl of a stand mixer, dissolve yeast in warm water. Stir in milk, 1/2 c. sugar, 1/3 c. butter, baking powder, salt, egg, and 2-3 cups of flour. Beat until smooth. Mix in enough remaining flour to make dough easy to handle (I usually use 5 1/2 - 6 cups). Turn dough onto a well buttered board. With buttered hands, knead dough until smooth and elastic.
Transfer dough to greased bowl. Cover and let rise until double, about 1 1/2 hours. Line two 9x12 pans with parchment paper and spray paper and pans with nonstick spray. Roll 1/2 of dough into a 12"x10" rectangle. Spread with 2 Tbsp. of butter (if it's not soft enough, I just melt it and smear it around). In a small bowl, mix granulated sugar, brown sugar, and cinnamon. Sprinkle half over dough. Roll up beginning at wide side. Pinch side to seal. Cut into 12 slices and place slices evenly in pan. Wrap tightly in foil. Repeat with the other half of the dough. Refrigerate at least 12 hours but no longer than 48 hours. (To bake immediately, cover and let rise until double.)
Heat over to 350F degrees. Remove foil. Bake 30-35 minutes until lightly browned.
Mix butter, powdered sugar, and vanilla. Add hot water 1 Tbsp. at a time until icing reaches desired consistency. Spread over warm (not hot) rolls.