Start the dough by adding ¾ cup (100 grams) of flour along with the sugar, instant rise yeast, cinnamon, salt, nutmeg, and allspice to the bowl of stand mixer fitted with a dough hook and stir to combine. Set aside.
To a small saucepan, add the butter and place over low heat. Cook until the butter is almost fully melted, then add milk and heat to 120-130 degrees F. Pour the mixture into the stand mixer and mix with a spatula until it just start to come together.
Add the remaining 2 ¾ cups (340 grams) of flour, 2 eggs (lightly beaten), raisins, and vanilla to the stand mixer bowl. Turn on the lowest setting and mix for about 5-6 minutes. Remove the dough hook and scrape any excess dough off of it and back into the bowl.
Cover the bowl with a kitchen towel and allow the dough to rest for about 10 minutes. *Pro Tip: I like to let the dough rise in my oven with the light on to have a bit more consistency and control on the temperature. (The oven should not be turned on.)
Lightly grease 9-inch x 13-inch ceramic baking dish. Divide the dough into 12 equal portions, roll them into balls, and place them into the dish. (I like to weigh the dough on a scale and divide the total weight by 12. Then I weigh each ball to keep them as even as possible.)
Cover the baking dish with a kitchen towel and allow the dough balls to double in size, about 45 minutes. (Again, I do this in my oven with the light on). Once doubled in size, remove the buns from the oven if you had them in there to proof.
Preheat the oven to 375 degrees F. Beat the remaining egg in a small bowl and brush the egg wash over the top of the buns.
Create the flour cross mixture by mixing the flour and water in a small bowl. Place the mixture into a piping bag (or food storage bag) and cut the tip off. Run a horizontal line of the flour mixture over each row and then pipe a vertical line to make a cross on each bun.
Bake the buns for about 18-20 minutes, until nicely golden on the top.
Carefully remove the dish from the pan and trasnfer the buns to cool on a wire rack to cool for at least 30 minutes.
Make the icing by combining the powdered sugar, milk, and orange zest in a small mixing bowl. Put the icing in a piping bag. Pipe the icing over the buns following the lines of the flour cross and enjoy!