Heat water to between 105 and 115 degrees F, remove from heat and transfer to a medium bowl, sprinkle in the yeast. Stir to dissolve and let sit for 5 minutes.
Whisk in the milk, butter, egg yolk, sugar, and vanilla into the yeast mixture until combined.
In a separate, large bowl, whisk together the flour, salt, nutmeg, and cinnamon.
Pour the wet ingredients into the dry ingredients and mix together with a wooden spoon until combined.
Transfer to a stand mixer fitted with a dough hook (or you can knead by hand) and mix on low speed for 8 minutes.
Add the raisins and mix for 1 more minute.
Spray a large bowl with cooking spray, form the dough into a large ball and place the dough in the bowl, cover with a dishcloth and place in a warm area to rise for 1 hour or until the dough has doubled in size.
Punch the dough back down, recover with the dishcloth, and let rise for 15 more minutes.
Preheat the oven to 375 degrees F and grease a 9x9-inch baking pan with non-stick spray.
Divide the dough into 9 equal pieces and use your hands to work the dough into buns with rounded tops, place the buns in the pan and bake for 23 to 25 minutes or until the tops are golden brown.
Remove from oven and prepare the icing, add the icing while the buns are hot and serve immediately.