3/4 cup butter, softened
1/2 cup white sugar
1 cup light brown sugar
1 teaspoon vanilla extract
1 1/4 cups all-purpose flour
1 teaspoon baking soda
1/2 teaspoon kosher salt
3 cups old-fashioned rolled oats
1 2/3 cups (approximately 11 oz) butterscotch chips
Preheat oven to 350 degrees. In a large bowl, beat the butter until smooth and almost fluffy, about 2 minutes. Add the sugars and continue beating until the mixture is light and fluffy, about 4-5 minutes. Add the eggs and vanilla and beat until smooth again.
In a separate bowl, whisk together all of the dry ingredients except the butterscotch chips. Gradually add this mixture to the wet ingredients, half at a time. Stir until fully combined. Add the butterscotch chips and stir well.
I used a medium size cookie scoop (about a tablespoon in size) to drop the dough onto a large baking sheet lined with a silpat mat. Bake for 8-9 minutes. Remove from the oven before the cookies are browned and when they still look soft in the center. Let them cool on the same tray for 5-10 minutes; this will allow them to finish baking without overcooking.
When the cookies are firm enough to handle, transfer them to a wire cooling rack and let cool completely. The finished cookies freeze well and the dough also freezes well. When I am baking the cookie dough straight from the freezer, I allow a few extra minutes for the baking.