Grab a handheld or electric mixer. Whisk these ingredients into the mixture and beat until smooth with each addition: soft butter and sugars (2 minutes, medium speed), eggs (1 minute, high), molasses, and vanilla (2 minutes, high). Set the bowl aside.
Mix flour, cinnamon, baking soda, and salt in another bowl. Slowly add it to wet ingredients (from Step 1). Mix at low speed until combined. Toss in the raisins and oats (and walnuts) and beat evenly.
Let the thick, sticky dough chill in the fridge for 30 minutes to an hour.
Preheat your oven to 350°F. Line your baking sheets with silicone mats or parchment paper.
Roll the dough into balls. Aim for 2 tablespoons of dough for each cookie. Space them on your prepared baking sheets (about 2 to 2.5 inches apart).
Bake them for 12 to 14 minutes until tender brown on the edges but still soft in the middle.
Let them cool on the baking sheet for 4 to 6 minutes before plopping them onto a wire rack to chill completely. Enjoy!