Preheat your oven to 180°C (350°F) and line a baking sheet with parchment paper or a silicone mat.
In a large mixing bowl, beat together softened butter and brown sugar until the mixture is light, fluffy, and slightly creamy, about 2-3 minutes. You’ll hear gentle mixing sounds and see the mixture turn a paler color.
Add the egg and vanilla extract to the butter-sugar mixture, beating until fully incorporated and the mixture is smooth. It should look slightly glossy and feel soft.
In a separate bowl, whisk together the rolled oats, flour, baking soda, and cinnamon until evenly combined. This creates a fragrant, speckled dry mixture.
Gradually add the dry ingredients to the wet mixture, mixing on low speed just until the ingredients are combined. The dough will start to come together and become thick and slightly sticky.
Gently fold in the raisins, distributing them evenly throughout the dough. If your raisins seem dry, soak them in warm water for 10 minutes first, then drain and add.
Using a cookie scoop or tablespoons, portion the dough onto the prepared baking sheet, spacing each mound about 2 inches apart to allow for spreading. The dough should look slightly rounded and rustic.
Bake in the preheated oven for 10-12 minutes, or until the edges are golden brown and the cookies have cracked slightly on top. Your kitchen will fill with the warm aroma of cinnamon and oats.
Once baked, remove the cookies from the oven and let them rest on the baking sheet for about 5 minutes. They will firm up slightly as they cool, with edges crispy and centers chewy.
Transfer the cookies to a wire rack to cool completely. Finish with a light sprinkle of sea salt or a drizzle of honey if you like, then enjoy their fragrant, chewy goodness.
