Stir the active dry yeast and the 2 grams of granulated sugar into the warm water and let it sit for 5 to 10 minutes until the surface is foamy and domed. If nothing happens in that time the yeast is no longer alive and the batch will not rise, so open fresh yeast and start the bloom again.

Whisk the bread flour, fine sea salt, and 18 grams of granulated sugar together in a bowl and set it aside.

Warm the Greek yogurt for about 40 seconds until it is just warm to the touch. It should never feel hot, because hot yogurt will kill the yeast you just woke up.

Add the warmed yogurt, the eggs, and the bloomed yeast to the bowl of a stand mixer fitted with the dough hook and mix briefly on low to combine.

Add the whisked dry ingredients and mix on low for about 2 minutes, until the dough comes together in a shaggy mass with no dry flour left in the bottom of the bowl.

With the mixer running on low, add the softened butter one tablespoon at a time, letting each piece disappear into the dough before the next one goes in.

Knead on medium for 6 to 8 minutes, until the dough is smooth and elastic and pulling away from the sides of the bowl. It should feel slightly tacky but not sticky. If it is still slack after the full knead, add flour only 10 grams at a time and only then, because this dough needs the whole knead before it firms up.

Transfer the dough to a lightly oiled bowl, cover it, and let it rise for 1 to 1.5 hours, until it has doubled in size.

Working with one rested log at a time, roll it out with a rolling pin into a rectangle about 8 inches wide and about 5 inches deep and a third of an inch thick, squaring the corners as you go.

Starting at the long edge farthest from you, roll the rectangle up one turn at a time, pressing the seam closed at every single turn so no air gets trapped inside. Pinch the final seam shut and pinch both ends closed.

Give the roll one or two passes under flat palms to even it out, easing off the pressure through the last inch and a half at each end so the ends stay blunt instead of tapering to points. The finished roll should be about 8 inches long.

Lay firmly rolled ropes of aluminum foil, or metal cannoli tubes wrapped in foil, across a half sheet pan about 3 inches apart, then lay one sheet of parchment flat over the top without pressing it down into the gaps. Set each shaped roll seam side down into a gap, where its own weight will settle the parchment into the valley and the tubes will act as walls that push the rolls up instead of out.

Cover the rolls and let them proof for 45 minutes to 1 hour and 15 minutes, until they are 50 to 75 percent larger rather than fully doubled. Poke the side of a roll to test it, and look for a dent that springs back slowly and only partway.

Preheat the oven to 375 degrees F during the last 20 minutes of the proof, and uncover the rolls when you turn the oven on so any condensation dries off the tops. Do not chill these rolls before baking, because the cold slows the oven spring and the rolls come out smaller and expand unevenly.

Whisk the egg yolk and the heavy cream together, then apply the wash to the tops and sides of the rolls with a folded paper towel, which lays down a thin even coat without dragging on the soft surface. Let the wash sit for about 2 minutes at room temperature so it tacks up.

Score each roll with a razor held close to vertical rather than angled, cutting about three eighths of an inch deep. Make three or four short diagonal cuts about 2 inches long, set about 45 degrees off the long axis of the roll, and stop about an inch from each end.

Bake uncovered at a steady 375 degrees F for 24 to 27 minutes, rotating the pan halfway through, until the rolls are deeply golden and the internal temperature reads 190 to 195 degrees F.

Move the rolls to a cooling rack and let them cool completely before slicing. Do not brush them with butter after baking, because it softens the crust and dulls the shine you just built with the egg wash.