Preheat oven to 375 degrees F convection. See recipe notes for non-convection.

To the bowl of a stand mixer using the paddle attachment (or using a hand mixer), beat the softened butter until light and fluffy for about a minute. Add the brown sugar and granulated sugar. Cream together until fluffy and smooth.

Crack the egg and add it to the butter/sugar mixture. Whip together with the beaters until the egg is fully incorporated. Add the sourdough discard, peanut butter and vanilla extract, mixing with each addition until smooth and combined.

To a medium-sized bowl, add the flour, cornstarch, baking soda and salt. Whisk together to combine.

Add the flour mixture to the butter mixture and mix until the wet and dry ingredients are incorporated.

Scoop the cookie dough into small, 2 Tablespoon sized balls and stick on a parchment lined baking sheet.

Bake cookies in a preheated, 375 degrees F oven on convection bake for about 7-8 minutes. After 7-8 minutes, the cookies should be puffy with the edges just a little crispy. If you don't have convection bake, bake the cookies at 375 degrees F for about 8-10 minutes.

While the cookies are baking, unwrap a hershey's kiss for each cookie. As soon as the cookies come out of the oven, place a hershey's kiss directly in the center of the cookie and press down just a little.

Let the cookies cool on a baking sheet for 5-10 minutes until they set up completely. Enjoy!