Preheat oven to 375.

In a stand mixer, beat butter and shortening together until combined (about a minute). Add sugars and beat another minute or two. Add vanilla and egg. Beat again.

Mix in the chocolate chips.

Add the flour, soda, and salt. Mix JUST until combined. It will look over-floured for a few seconds, but should come together fairly quickly.

Scoop golf-ball size spoonfuls of dough onto cookie sheet, sprinkle each ball with a pinch of kosher or sea salt and bake for 9-11 minutes (mine are 11 minutes, every time, except when I've made them in a higher altitude like Utah, and there it's about 9 minutes). They should be light-colored and puffed when they come out of the oven, but dry-looking (not shiny or wet). Let cool on the pan for about 5 minutes then transfer to cooling rack.