In a large bowl, mix together 2 cups of the bread flour, the hot water, and 1/4 teaspoon of the yeast. Use a fork to mix until a shaggy dough forms. Cover, and let rest for 20 minutes.

In the bowl of a stand mixer, beat together the butter and the all-purpose flour on medium for about 3 minutes, until creamy. Use a rubber spatula to scrape out the mixture onto a sheet of parchment or wax paper, and set aside at room temperature. Wipe out the bowl of the mixer.

Place a dough hook on the mixer. Add the shaggy dough you made earlier to the bowl of the mixer. Add the remaining 2 1/2 cups bread flour, the last 3 teaspoons of yeast, the brown sugar, salt, and warm milk. On the lowest speed, knead until evenly incorporated, then increase the speed to medium-high for 3-5 minutes, until the dough pulls cleanly away from the sides of the bowl. It will still be wet and sticky.

Dust a large surface liberally with flour, and scrape the dough onto the floured surface. Lightly sprinkle the dough with more flour, and roll it out into a rectangle 10 inches wide and 13 inches long. Roll it out some more until it is about 33 inches long, dusting the countertop with more flour as needed to prevent sticking. Use a knife or an offset spatula to spread the reserved butter and all-purpose flour mixture evenly onto the rectangle of dough, all the way to the edges. Use a dough scraper (or your hands, if you don’t have one) to lift up one end of the dough, and fold it over five times until you reach the end of the dough, resulting in a rectangle about 10 inches by 6 inches. Pinch the ends of the dough together to seal, then rotate the rectangle 90 degrees and roll it out again to 10 inches wide and 33 inches long. Fold it over five times until you reach the end of the dough, and transfer it to a floured sheet pan. Cover with plastic, and refrigerate for at least 1 1/2 hours, or up to overnight.

Preheat oven to 400ºF. Butter 6 ramekins or extra-large muffin cups, or 12 regular-sized muffin cups. Set aside.

In a small bowl, stir together half of the lemon zest, vanilla bean seeds, poppy seeds, cinnamon, and sugar. Set aside.

Transfer the dough to a floured surface, and roll it into a rectangle 18 inches long by 10 inches wide. In an even layer, sprinkle the poppy seed-sugar mixture over the dough. Tightly roll the dough (lengthwise) into an 18-inch long log. Use a serrated knife to cut the log into six (or 12, if using smaller muffin cups) even segments. Place the buns into the prepared ramekins or muffin cups, and cover with a clean, damp towel. Let rest for 30-45 minutes, until they puff up a bit.

Bake for 30 minutes, or until golden and puffed up. After the first 20 minutes, check to make sure the tops are not browning too fast—if so, lower the heat to 380ºF for the last 10 minutes of cooking time.

In a small saucepan, combine the blueberries with a tablespoon of water. Cook, stirring, over medium heat, until it forms a syrup. Strain the blueberries and reserve the syrup. In a small bowl, whisk together the syrup and powdered sugar, 2 tablespoons of Meyer lemon juice, and vanilla extract. Thin with more lemon juice to achieve desired consistency (you will have lemon juice left over).

Drizzle the morning buns with lemon-blueberry glaze, sprinkle with remaining Meyer lemon zest, and serve warm.