In a large bowl, whisk together water, yeast, and sugar. Let sit for 5-10 minutes until foamy. Using a whisk, mix in half the flour, the salt, spices, sugar, butter, and orange zest. With a wooden spoon, stir the mixture and add enough flour to make the mixture soft and pliable (but not sticky). Add the currants, then knead the dough until elastic. Place in a large, greased bowl. Cover with a towel and allow to rise in a warm, dry location for about 1 hour, or until double in bulk.
Separate dough into 18-24 small pieces. Roll into balls and place on a parchment-lined baking sheet. Use a pastry brush to brush the top of each roll with egg & milk mixture. Allow rolls to rise until double in bulk, about 45 minutes.
Preheat oven to 350 degrees. Bake rolls in preheated oven for 16-22 minutes, or until light golden brown. Remove and cool completely before frosting.
For frosting: beat together butter, powdered sugar, and milk. Place in a pastry bag. Pipe in a cross over the top of each cooled bun. Serve and enjoy!