In a large bowl, combine currants and hot orange juice. Cover with plastic wrap, and let stand for 20 minutes. Using a fine-mesh sieve, strain currants, discarding excess liquid.

In the bowl of a stand mixer, combine warm milk, ½ cup (120 grams) warm water, ¼ cup (50 grams) sugar, and yeast. Let stand until foamy, about 10 minutes.

In a large bowl, whisk together 2⅔ cups (333 grams) flour, salt, cinnamon, nutmeg, allspice, and remaining ¼ cup (50 grams) sugar. Add flour mixture to yeast mixture, and using the paddle attachment, beat at low speed just until combined. Beat in melted butter and 2 eggs (100 grams). Add currants and candied orange peel, and beat until combined. Gradually add 2⅔ cups (333 grams) flour, beating until combined; scrape sides of bowl

Switch to the dough hook attachment. Beat at low speed until a smooth, elastic, slightly tacky dough forms, 4 to 6 minutes, adding up to ⅓ cup (42 grams) flour, 1 tablespoon (8 grams) at a time, if dough is too sticky. Turn out dough onto a lightly floured surface, and shape into a smooth round.

Spray a large bowl with cooking spray. Place dough in bowl, turning to grease top. Loosely cover and let rise in a warm, draft-free place (75°F/24°C) until doubled in size, about 1 hour.

Spray a 13×9-inch rimmed baking sheet with baking spray with flour.

Lightly punch down dough, and let stand for 5 minutes. Turn out dough onto a lightly floured surface, and divide into 12 portions (about 128 grams each). Roll each portion into a ball. Place about ¼ inch apart on prepared pan. Cover and let rise in a warm, draft-free place (75°F/24°C) until puffed, buns are touching, and dough holds an indentation when poked, about 40 minutes.

Preheat oven to 375°F (190°C).

In a small bowl, whisk remaining 1 egg (50 grams). Brush tops of rolls with egg.

Clean bowl of stand mixer and paddle attachment. Using the paddle attachment, beat room temperature butter and remaining ½ cup (63 grams) flour at medium-low speed; slowly add orange blossom water and ½ teaspoon (2.5 grams) water, beating until a thick paste forms and stopping to scrape sides of bowl. Spoon paste into a pastry bag, and cut a ¼-inch opening in tip. (Alternatively, use a pastry bag fitted with a ¼-inch round piping tip [Ateco #802].) Pipe paste on top of buns in continuous lines following curves of rolls to form a cross over each.

Bake until golden brown and an instant-read thermometer inserted in center of a bun registers 190°F (88°C) to 200°F (93°C), 24 to 30 minutes, loosely covering with foil during final 2 to 5 minutes of baking to prevent excess browning. Serve warm or at room temperature.