2 cups flour
3 teaspoons baking powder
1 teaspoon salt
6 tablespoons unsalted butter
2/3 cup milk
4 tablespoons unsalted butter, softened to room temperature
1/4 cup sugar
3 teaspoons cinnamon
2 tablespoons butter, room temperature
1 cup powdered sugar
1/2 teaspoon vanilla extract
Preheat oven 425 degrees F.
Whisk together the dry ingredients. Cut in the butter with a pastry cutter, or pulse mixture in a food processor. Add milk. Stir together and knead lightly to form a dough. Roll dough out on a lightly floured surface to about a 1/4-inch thick in a rough rectangle.
Using a spatula or butter knife spread the softened butter evenly over the surface of the dough. Sprinkle the sugar and cinnamon evenly over dough. Roll up dough tightly like a jelly roll (from the longest side). Cut into 1-inch pieces and place cut-side down on a parchment-lined cookie sheet or sheet pan. Bake for about 15 minutes until golden.
Make the glaze: Flatten the soft butter in a medium mixing bowl. Add the powdered sugar and mix with the butter. Add a few tablespoons of very hot water, stirring briskly, until a nice icing consistency forms. Stir in the vanilla extract. When the buns are cooled, slather some glaze on top of each one with a knife or spatula.