Preheat the oven to 350 and grease a doughnut pan. *If you do not have a doughnut pan, you can use a muffin pan and make these into muffins. In a large bowl, combine the flour, cornstarch, cinnamon, baking powder, baking soda, and salt.
In a separate bowl, combine the unsalted butter and sugar. Cream together until smooth.
Stir in the eggs and egg yolks until well blended.
Fold the dry ingredients from the large bowl, into the wet ingredients.
Add in the apple cider, make sure you do not over mix.
Spoon the batter into the doughnut pan and bake in the preheated oven for about 8-10 minutes.
Remove pan from oven and allow to cool in the pan for at least 5 minutes.
While donuts are cooling, prepare the glaze.
In a small bowl, whisk together the powdered sugar, corn syrup, and pinch of salt.
Add in the boiling water, 1 tablespoon at a time, until icing comes together.
In a medium saucepan, combine the sugar and water over high heat. Bring to a rapid boil and allow to cook for 8 minutes, or until a amber color starts developing.
Remove from heat and slowly pour the heavy cream into the mixture.
Stir the caramel into the heavy cream mixture and stir to combine.
Dip the tops of each doughnut into the glaze and sprinkle salt over the top of each glaze covered doughnut.
Allow glaze to firm up a bit on doughnuts, and enjoy!!