Start by soaking the raisins in warm water for about 10–15 minutes. This softens them and keeps them from drying out during baking. Once they’ve plumped up, drain and pat them dry with a paper towel.

In a large mixing bowl, cream the softened butter, brown sugar, and granulated sugar until light and fluffy. This should take about 2–3 minutes with a mixer on medium speed. Add the eggs one at a time, beating well after each addition, and then mix in the vanilla extract.

In a separate bowl, whisk together the flour, baking soda, cinnamon, and salt. Slowly add the dry mixture to the wet ingredients, mixing just until combined. Fold in the oats and then gently stir in the raisins. If you’re using nuts, add them at this stage as well.

Cover the dough and chill it in the refrigerator for at least 30 minutes. Chilling is crucial because it helps firm up the dough, prevents spreading, and intensifies the flavor.

Preheat your oven to 350°F and line two baking sheets with parchment paper. Using a cookie scoop or spoon, drop dough onto the prepared sheets, spacing them about two inches apart.

Bake the cookies for 10–12 minutes, or until the edges are golden and the centers are just set. They may look slightly underbaked in the center—that’s okay. Let them cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.