Position the oven racks in the top third and center of the oven and preheat the oven to 375 degrees F. Line 2 large rimmed baking sheets with parchment paper or silicone baking mats.
To make the filling: In a small bowl, mix the butter, brown sugar, and cinnamon until smooth.
To make the dough: In a large bowl, whisk together the flour, sugar, baking powder, and salt. Using a pastry blender or your fingertips, work in the butter until the mixture is crumbly with some pea-sized pieces of butter. Do not overmix. Mix in the raisins. Stir in the half-and-half and mix just until the dry ingredients are moistened. On a lightly floured work surface, roll out the dough into a 17-by-12-inch rectangle about 1/4-inch thick. Spread the cinnamon filling evenly over the top of dough, leaving a 1/2 -inch border on all four sides. Starting at a long side, tightly roll the dough up into a log. Cut the dough into 2-inch slices and arrange them, cut sides up, 4 inches apart on the prepared baking sheets. Bake, switching the positions of the baking sheets from front to back and top to bottom halfway through baking, until the rolls are slightly golden, 25 to 30 minutes. Let cool on the pans for 10 minutes.
To make the icing: In a small bowl, mix the confectioners' sugar and water with a fork until smooth. Drizzle over the buns. Serve warm, or let cool to room temperature.