In a stand mixer or large bowl, add the shortening, softened butter, brown sugar, and white sugar. Mix on low speed until the mixture is light and fluffy.
Add in the well-beaten eggs and vanilla. Mix well until fully combined. (If desired, add 1/2 cup of chopped nuts at this time.)
Pour in the flour and baking soda and mix until just combined. Avoid overmixing the batter.
Fold in the oatmeal and butterscotch chips using a stiff spatula to avoid overmixing. (*See note below on butterscotch chips.)
Using a 1.5 tablespoon cookie scoop, drop the dough onto a baking sheet lined with parchment paper. Gently roll each one in your hands to create round dough balls. Bake the cookies for 14 to 16 minutes or until the edges start to turn golden brown. The middle might be slightly gooey still.
Allow the cookies to cool fully, then store in an airtight container.
Notes
*I like to reserve about 1/4 cup of butterscotch chips. Once the cookies are baked, I immediately add a few chips to the top of each cookie. This helps to give you that "picture-perfect" appearance.