Preheat the oven to 350°F (180°C) and line 3 baking trays with parchment paper. For this recipe, I did fan assist* as there will be multiple trays in the oven, and you will want them to bake evenly.

Using a stand mixer or electric hand mixer, cream the softened butter on high speed for 2 - 3 minutes, until really light and fluffy.

Add in the powdered sugar and continue creaming until the mixture is light and fluffy and there are no lumps, about 3 minutes.

Slowly add in the egg whites and whole egg and mix until smooth. Lastly, add the vanilla. (If the mix curdles don't worry, just give it a good whisk to bring it back together.)

Once combined, add the flour and salt and mix until it just comes together. Do not overmix. The batter will be somewhat soft.

Scrape sides of the bowl in order to place batter in a piping bag fitted with a medium pastry tip. Pipe it in even mounds onto baking trays (roughly 2 teaspoons.) Keep cookies about 1 ½-inches apart as the batter will spread when baked.

Place the trays in oven and bake for about 18-20 minutes or until golden. Rotate the trays as needed.

Once cooled, store in an airtight for up to 7 days. Use for a cookie crust or for a classic banana pudding.