In the bowl of a stand mixer fitted with the dough hook attachment, lightly combine the flour, yeast, ginger, cinnamon, salt, mace (or nutmeg), and allspice.
Combine the milk, molasses and melted butter in a small saucepan and heat until a thermometer registers between 120 and 130℉ (you can do this in the microwave if you prefer). Turn the mixer on low speed and slowly drizzle the warm milk mixture into the flour mixture. Add the granulated sugar and beat for about 2 minutes, or until the dough comes together. Transfer dough to a lightly floured surface, and with floured hands, knead for 6 minutes. The dough should be smooth and elastic.
Spray a large mixing bowl with cooking spray. Place the dough in the bowl, turning to coat both sides. Cover with plastic wrap and let rise in a warm, draft-free place for at least 1 hour, probably closer to 2 hours, until doubled in size. I set my bowl on a chair right next to but not touching the radiator. Every time I made this I had to proof closer to 2 hours - the molasses really slows the yeast.
During this first rise, generously butter a 12-inch cast-iron skillet (or you can use a similar-sized baking dish or other oven-proof skillet).
Gently gather (do not punch) down the dough and transfer it to a lightly floured work surface. Cut the dough in half. Using a floured rolling pin, roll one half of the dough into a 12x16-inch rectangle. Spread half of FILLING onto dough (I’ve found a small offset spatula works best). Leave a small - roughly an inch - border around the edges of the dough. Starting with one long side, tightly roll the dough and pinch the seams together. With a serrated knife, cut the dough into six even pieces (do your best, then don’t worry). Place the pieces, cut side up, in the prepared skillet. Repeat with the second half of the dough.
Cover the skillet and let dough rise again in a warm, draft-free place for 30 minutes. Meanwhile, preheat your oven to 350℉. Bake until golden brown, 25 to 30 minutes. When they are done, they’ll sound hollow when tapped and the middles will not be smushy when pressed.
Let cool 5 minutes then drizzle liberally with the glaze. Serve warm. Or room temperature. Or both.