Combine warm milk and yeast in a large mixing bowl. Let sit for 5 minutes while yeast dissolves. Meanwhile, combine 3 cups Bob’s Red Mill Unbleached White All-Purpose Flour, salt, sugar, and spices in a bowl and set aside.
Add melted butter, egg, vanilla extract, and flour mixture to the yeast. Mix until a shaggy dough forms, about 2 minutes with a dough hook in a stand mixer or 4 – 5 minutes by hand.
Add currants and knead until a smooth and elastic dough forms, about 9 minutes in a stand mixer at medium speed or 10 – 15 minutes by hand. Add remaining ½ cup flour only if needed to make a workable dough. Shape dough into a ball.
Place dough in a large bowl lightly coated with oil; turn once to coat both sides. Cover and set aside in a warm place to rise until doubled in size 60 – 90 minutes. Meanwhile, line a baking sheet with parchment paper and set aside.
Turn the risen dough out onto a lightly floured surface and divide into twelve equal pieces, about 2 oz of dough per piece. Shape each piece into a tightly formed bun and place seam-side down on the prepared baking sheet. When all buns are formed, cover and let rise in a warm place until doubled in size, about 45 minutes. Meanwhile, preheat oven to 375°F.
For the wash, combine egg and water and mix well. Once buns have doubled in size, gently brush the top and sides of each bun with egg wash. Bake until buns are deep golden and the interiors have reached 190°F, about 25 minutes. Let cool at least 30 minutes before icing.
For icing, combine all ingredient and mix until smooth. Drizzle a cross over each cooled bun.
