Whisk the flour, cinnamon, baking soda, and salt together in a medium bowl. Set aside.

In a large bowl using a hand mixer or a stand mixer fitted with a paddle attachment, beat the butter, brown sugar, and granulated sugar together on medium-high speed until combined and creamy, about 2 minutes. Add the eggs, molasses, and vanilla and beat on high speed until combined, about 1 minute. Scrape down the sides and up the bottom of the bowl and beat again as needed to combine.

Add the dry ingredients to the wet ingredients and mix on low until combined. With the mixer running on low speed, beat in the oats and butterscotch morsels. Dough will be thick and sticky. Cover and chill the dough for at least 45 minutes in the refrigerator (and up to 4 days). If chilling for longer than a few hours, allow to sit at room temperature for at least 30 minutes before rolling and baking because the dough will be quite hard.

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

Scoop cookie dough (here’s the large cookie scoop I love), about 3 Tablespoons of dough per cookie, and place 4 inches apart on the baking sheets. Bake for 13-14 minutes or until lightly browned on the sides. The centers will look very soft.

Remove from the oven and allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely. While the cookies are still warm, I like to press a few more butterscotch morsels into the tops—this is only for looks!

Cookies stay fresh covered at room temperature for up to 1 week.