In-N-Out Burger's delicious shakes are made with real ice cream, and that's a good thing,  but this vanilla shake has a unique taste that's more than just straight vanilla—I sense a hint of buttery caramel. Riffing on that idea I came up with an easy hack for these tasty shakes using a blend of French vanilla ice cream and whole milk, along with a simple secret ingredient: caramel topping. Spooning just 1 tablespoon of Smucker’s caramel topping into the blender before mixing it all up produced a vanilla shake remarkably similar to the one that’s been served at In-N-Out Burger since 1975.

Unfortunately, a milkshake produced with a home blender is thinner than a restaurant milkshake made with a milkshake machine. To fix that, after mixing your shake in the blender, place the blender in your freezer for a bit until the shake firms up, then mix it once again, spoon it into a tall glass, and serve it with a wide straw.

This In-N-Out Double Double recipe makes a homegrown clone of what I believe is the best hamburger in the world. The ingredients are fresh, and simple and the stacking order is crucial. Certainly one of the secrets to duplicating this and other fast food burgers is getting the beef patties super thin—about 1/4 inch-thick. As for the secret sauce in this In-N-Out burger recipe, Kraft thousand island dressing will do.

Source: Top Secret Recipes by Todd Wilbur.

Update 3/24/18: Get an updated re-tooling of this entire recipe with better spread, new secrets, and lots of photos on my Food Hacker blog.