Preheat the oven to 350F.
In a large mixing bowl, sift together the pastry flour, salt, baking powder, and baking soda. Whisk together and set aside for later.
In a separate mixing bowl, whisk together the champagne, applesauce, sugar, oil, and vanilla bean paste/extract.
Next, add the bowl of dry ingredients to the bowl of wet ingredients and mix together until a thick batter is formed.
Spray the donut pan with a cooking spray and then fill with each donut with batter until ¾ full, making sure not to cover the center hole with any batter.
Bake for 11-13 minutes until the donuts are beginning to brown and are cooked through.
Remove from the oven and let rest in the pan for about 5 minutes. Then, flip the donut pan upside down onto a cooling rack and let the donuts cool completely before dipping into glaze.
Once the donuts have cooled, make the glaze by whisking together the powdered sugar with the 4 tsp champagne in a small bowl.
Dunk each donut into the glaze and then place back onto the cooling rack for 5-10 minutes until the glaze sets and solidifies. As an optional topping, add on some sparkly sprinkles before the glaze has set. Serve and enjoy!