Preheat oven to 375 F (Dr. T recommends 365 F convection if you’ve got it).
Cream together the shortening, butter and sugars. Beat in the egg and vanilla until creamy. If you are using a stand mixer you don't have to wait to put in the eggs and vanilla.
In a separate bowl, combine all the dry ingredients except the oats and chocolate chips.
Gradually add the dry mix to the shortening mix, beating well.
Stir in the oats and chocolate chips.
Spoon in large dollops onto two big, non-stick cookie sheets. As suggested by Pat in the comments, I use an ice cream scoop. Squash the dollops into rounds. I use my clean hands but if you want to use a utensil you might need to grease it. Let me know how it goes!
Bake about 8 minutes if you’re using convection, about 10-12 regular. If you are using convection you can bake both at the same time.
Put the cookie sheets on the cool stovetop or wire stands to cool for a few minutes until you can transfer the cookies to plates for further cooling without breaking.