Start by placing the diced apples, butter, and light brown sugar into a medium frying pan over medium-high heat. Stir occasionally, cooking until the apples are tender and turn a lovely golden hue—about 5 to 7 minutes. Once done, spread them out on a paper towel to cool down.

In a medium-sized bowl, combine the flour, baking soda, cinnamon, and salt. Whisk them together to ensure an even distribution. This is an important step that helps your cookies rise beautifully.

In the bowl of your electric mixer, add the softened butter, light brown sugar, and granulated sugar. Beat on medium-high speed for about 3 minutes until the mixture is light and fluffy. This step aerates the batter, yielding a delightful cookie texture.

Add the eggs to the butter-sugar mixture one at a time, making sure to mix well after each addition. Beat on high speed for about a minute until well combined, then add the vanilla extract. This will give your cookies a wonderful depth of flavor.

Next, lower the mixer speed and gradually add the flour mixture you prepared earlier. Mix until just combined, be careful not to overmix. Fold in the rolled oats gently, and then, finally, add the cooled apples (and walnuts, if using), mixing just enough to distribute throughout the dough.

Cover the cookie dough with plastic wrap or a kitchen towel and place it in the refrigerator for at least an hour. This allows it to firm up, making it much easier to scoop and bake later.

Preheat your oven to 350°F (175°C). Line your baking sheets with parchment paper for easy cleanup.

Using a medium cookie scoop, place the dough onto the prepared baking sheets about 2 inches apart. I usually fit around 6 cookies per sheet to give them enough space to spread.

Pop the trays in the oven and bake the cookies for 12 to 15 minutes. You’ll know they’re ready when the edges are golden brown, but the center still looks slightly set.

After taking them out of the oven, let the cookies sit on the baking sheet for about 5 minutes. This helps them firm up a bit. Then transfer them to a wire rack to cool completely. While they cool, you can mix the powdered sugar and water in a small bowl to create a glaze. Drizzle this mixture over the cooled cookies with a spoon for a sweet finishing touch.