First things first, let’s bloom the yeast! Combine the active dry yeast, sugar, and warm milk, then let it sit for about 10 minutes until it gets all foamy on top.
Meanwhile, in the bowl of a stand mixer fitted with a whisk attachment, mix together the flour, chai spices, salt, and sugar.
Add the whisked eggs, vanilla, and melted butter to the dry ingredients and mix it all together. Then, pour in the yeast mixture and blend until everything is combined. Switch to a dough hook and knead on medium speed for 7-10 minutes until the dough pulls away from the sides of the bowl, forms a nice ball, and springs back when you poke it.
Once you’ve got your dough, shape it into a ball and transfer it to a large, greased bowl. Cover it with plastic wrap or a kitchen towel, and let it rise in a warm spot (I use my toaster oven on the "proof" setting, if you don't have one of those turn your oven on preheat 350 for 1-2 minutes then turn it off, then place your dough in there) for about 1 to 1 ½ hours or until it doubles in size.