To begin, preheat your oven to 350 and spray a donut pan with non-stick spray.
To a large mixing bowl, add your butter and brown sugar and whisk together. Add your Greek yogurt, milk and egg and whisk together till smooth. Add your egg and briefly whisk it in.
To the same bowl, add your flour, baking soda, salt, cinnamon, ginger, cardamom and allspice and stir together till you have a smooth, consistent donut batter.
Fill each donut tin to just under the top of the lip. You can add your donut batter to a piping bag, if you prefer, to easily fill the donut pan.
Bake in the oven for 8-10 minutes, or till the tops are springy to touch and a toothpick inserted comes out clean.
Let cool. Run a knife around the outside edge of each donut and flip them onto a cooling rack.
To a small mixing bowl, add your sugar, cinnamon, ginger, cardamom and allspice and whisk together till all the spices are evenly incorporated throughout.
Brush the top and bottom of a donut with the melted butter and then swirl the donut around in the bowl of chai sugar topping. Flip it over to coat the other side. Continue till evenly coated all around.
Continue to brush each donut with butter and coat them in the chai sugar topping.
Devour!
I recommend putting the topping on just prior to serving. These last in the fridge for about a week, stored in an airtight container.