To make the dough: Whisk the dry ingredients together, then stir in the water, sour cream, eggs, and flavor. Mix and knead — by hand, mixer or bread machine — until you've made a very soft, smooth dough., Allow the dough to rise, covered, for about 1 to 2 hours; it'll become slightly puffy, but won't double in bulk., While the dough is rising, prepare the pan(s): use a 9" x 13" pan, or two 9" round pans., To make the topping: Spread the melted butter in the bottom of the pan, and sprinkle the sugars over it. Spread the diced nuts over the sugars., To assemble the buns: Transfer the dough to a lightly greased work surface, and roll it into a 16" x 20" rectangle. Spread it with the cinnamon filling, leaving an uncovered strip about 1" wide along one short edge of the dough., Starting with the filling-covered short edge, roll the dough into a log, and slice it into 16 slices, each about 1" wide., Place the buns in the prepared pan(s), leaving about 1/2" between them. Cover the pan(s), and let the buns rise for 90 minutes; again, they won't rise much, they'll just seem to spread a bit. Want to shape the buns, then refrigerate overnight and bake the next day? See "tips," below., Towards the end of the rising time, preheat the oven to 350°F., To bake the buns: Bake the sticky buns for 35 to 40 minutes, tenting them lightly with aluminum foil for the final 5 minutes if they appear to be browning too quickly. The finished buns will be golden brown., Remove the buns from the oven, loosen their edges with a knife, and carefully turn them out onto a rack or parchment-covered sheet pan to cool, scraping any glaze that may have stuck to the pan onto the warm buns., Serve warm, or at room temperature. Store leftovers at room temperature, well wrapped, for several days; freeze for longer storage.