Cream the softened butter and both sugars together on medium speed until smooth, about 2 minutes. Add the eggs and mix on high until combined, about 1 minute. Scrape down the sides and bottom of the bowl as needed. Add the vanilla and molasses and mix on high until combined. Set aside.

In a separate bowl, whisk the flour, baking soda, cinnamon, and salt together. Add to the wet ingredients and mix on low until combined. Beat in the oats, raisins, and walnuts (if using) on low speed. Chill the dough for 30-60 minutes in the refrigerator.

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

Roll balls of dough (about 2 tablespoons of dough per cookie) and place 2 inches apart on the baking sheets. Bake for 12-14 minutes until lightly browned on the sides. The centers will look very soft and under-baked. Remove from the oven and let cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.