To make the dough: Mix together all the dough ingredients except the salt (and yeast) until the flour is evenly moistened and the dough has formed a cohesive, sticky mass, 2 to 3 minutes on low speed of a stand mixer., Add the salt (and yeast) on top of the dough (without mixing it in), then cover and let the dough rest for 20 minutes. This rest is period is known as an autolyse., After the autolyse, mix in the salt (and yeast) until fully incorporated, about 1 minute on low speed. Turn the mixer up one speed and knead the dough until it’s smooth and supple though still somewhat soft and tacky, about 2 to 3 minutes., Cover the dough and let it rest in a warm (75°F) place for 4 hours. To develop strength in the dough, stretch and fold it in the bowl three to four times during the rest. You can be fairly flexible in your timing of these. One stretch and fold per hour is ideal. The goal is to end up with a strong dough with good elasticity., To make the filling: Meanwhile, combine all the filling ingredients in a medium bowl. The texture will be somewhat like wet sand., Turn the dough out onto a lightly greased or floured work surface and gently deflate it, patting or rolling it into a 14” x 20” rectangle., Spread the filling evenly over the surface of the dough, leaving 1/2” of exposed dough along one short edge., Starting with the filling-coated short edge, roll the dough into a log. As you roll, the log will lengthen to around 18"., Cut the log into twelve 1 1/2” slices and place them in a lightly greased 9” x 13” pan. Cover the pan and let the buns rise until they’re puffy, 2 to 3 hours., At this point, you can let the buns rise for another hour or so and then bake them; or you can place the pan in the refrigerator overnight, covered, and bake the buns the next day (up to 24 hours later)., To bake the same day: Bake the buns in a preheated 400°F oven for 18 to 22 minutes, until golden. A digital thermometer inserted into the center of a middle bun should read 190°F., To make the icing: While the buns are baking, stir together all the ingredients in a medium bowl until smooth., Remove the buns from the oven and cool for 5 to 10 minutes before icing. Alternatively, allow the buns to cool to room temperature. Cover the buns and leave them at room temperature overnight, then reheat in a 325°F oven for 10 to 15 minutes before icing and serving., To bake the buns after being refrigerated overnight: Remove the pan from the refrigerator and leave the buns covered at room temperature while you preheat the oven to 400°F., Bake the buns for 20 to 25 minutes, until golden. A digital thermometer inserted into the center of a middle bun should read 190°F. Remove the buns from the oven and cool for 5 to 10 minutes before icing., Wrap the buns in plastic and store at room temperature for a day or so; freeze unfrosted buns for longer storage.