Cream the butter and sugars together on medium speed for about 2 minutes until smooth and creamy. Then, add the eggs and mix on high for 1 minute, ensuring everything is well combined. Stir in the vanilla and molasses, mixing on high again until fully combined.

Whisk together the flour, baking soda, cinnamon, and salt in a separate bowl. Gradually add these dry ingredients to the wet mixture using low speed, mixing until just combined. Fold in the oats, raisins, and walnuts (if using) on low speed until evenly distributed. Chill the dough in the refrigerator for 30-60 minutes.

Preheat your oven to 350°F (177°C). Line two large baking sheets with parchment paper.

Scoop out balls of dough—roughly 2 tablespoons per cookie—and place them 2 inches apart on the baking sheets. Bake for 12-14 minutes, until edges are lightly browned. Let them cool on the baking sheet for 5 minutes before transferring to a wire rack.