Preheat and prep: Heat your oven to 350°F (175°C). Line two baking sheets with parchment paper for easy cleanup and even browning.

Cream the butter and sugars: In a large bowl, beat the butter, granulated sugar, and brown sugar until light and fluffy, about 2 minutes. This step adds air and helps with that soft, chewy crumb.

Add Nutella, egg, and vanilla: Mix in the Nutella until smooth. Beat in the egg and vanilla just until combined. Don’t overmix here—keep it creamy and uniform.

Incorporate the sourdough discard: Stir in the discard until fully blended. The dough will look glossy and soft, which is perfect.

Whisk dry ingredients: In a separate bowl, whisk together flour, baking soda, baking powder, and salt.

Combine wet and dry: Add the dry ingredients to the wet in two batches, mixing on low just until no dry patches remain. If using chocolate chips or nuts, fold them in now.

Scoop the dough: Use a medium cookie scoop (about 1 1/2 tablespoons) to portion mounds onto the prepared sheets, spacing them about 2 inches apart.

Bake: Bake for 9–11 minutes, until the edges look set and lightly browned but the centers still appear soft and slightly underdone. They will finish setting on the tray.

Optional swirl: For extra Nutella ribbons, dot a tiny 1/4 teaspoon of Nutella onto each hot cookie and swirl gently with a toothpick.

Cool and set: Let cookies rest on the baking sheet for 5–7 minutes, then transfer to a rack to cool completely. This step is key for that chewy texture.