Preheat and prep: Heat your oven to 350°F (175°C). Line a baking sheet with parchment paper.
Mix dry ingredients: In a medium bowl, whisk oats, flour, baking soda, cinnamon, and salt until combined.
Cream the butter and sugars: In a large bowl, use a hand mixer or sturdy whisk to beat the butter, brown sugar, and granulated sugar until sandy and well combined, about 1 minute. It won’t get fluffy—that’s okay.
Add wet ingredients: Mix in the egg white, applesauce, and vanilla until smooth.
Scrape down the sides of the bowl.
Combine: Add the dry ingredients to the wet. Stir with a spatula until just combined. Fold in the raisins (and optional mix-ins).
Chill (important): Refrigerate the dough for 20–30 minutes.
This helps prevent spreading and keeps the cookies thick and chewy.
Scoop and shape: Use a 1-tablespoon scoop to portion the dough into 16 balls. Place on the baking sheet, spacing about 2 inches apart. Gently flatten the tops with damp fingers to about 1/2 inch thick.
Bake: Bake 9–11 minutes, until edges are set and centers look slightly underdone.
They’ll finish setting as they cool.
Cool: Let cookies rest on the sheet for 5 minutes, then transfer to a wire rack to cool completely.