Preheat the oven to 350F. Grease 2 standard donut pans (spray lightly with oil). Set aside.
In a medium mixing bowl, combine and whisk the dry ingredients: flour, cornstarch, powdered sugar, granulated sugar, baking powder, sea salt, and allspice.
In a 2 cup glass measuring cup, or heat safe bowl, combine the milk and butter. [You can reuse the measuring cup later on too.] Microwave until the butter melts into the milk. This mixture should be warm but not hot. Be sure to stir the mixture well before adding into the dry ingredients.
After adding the milk-butter mixture to the dry ingredients, add the vanilla extract. Stir gently with a spoon until the mixture is combined. Try not to over mix the batter, some small lumps are ok.
Pour the batter back into the 2 cup measuring cup, and pour into the prepared donut pan about 3/4 full per donut. Alternatively, you can spoon the batter into the donut pan. However, this is quite a wet batter so that may be challenging.
Bake 10 to 13 minutes until done. The internal temperature should read about 190 to 200F. The donuts might be very blonde looking still which is alright as long as they are cooked through. The tops will also spring back if you gently push down.
Allow to cool for a couple minutes in the donut pan, then remove to a wire cooling rack.
While the donuts are cooling, get a sandwich sized ziploc bag and add about 3/4 cup powdered sugar. Donuts are ready to be coated in powdered sugar while they are warm-cool. Do NOT add hot donuts to the powdered sugar as this will just melt the sugar and the coating will be invisible. You also do NOT need to spray with oil or dip in butter before the sugar coating. This will create a wet mess.
One at a time drop donuts into the bag of powdered sugar, seal it shut then shake gently until the donut is fully coated.
Remove donut and repeat process with remaining donuts.
Serve fresh, preferably same day since the powdered sugar will disappear overnight ;)
