Salted Butter Caramel Sauce

Adapted from The Perfect Scoop, Revised and Updated

This sauce is easy to make. The trick is to get the caramel base as dark as possible, in step #2, close to burnt, but not quite. The caramel will start to smoke, and a few seconds later, will smell rich and caramelized. That's the moment to remove it from the heat and add the cream. For more guidance and photos, check out my post: How to make the perfect caramel. If you wish to use unsalted butter, you can add an additional scant 1/4 teaspoon of flaky salt to the finished sauce, or to taste. A few readers found the sauce to be on the salty side (I use fleur de sel de Guérande), but sea salts can vary. So you might want to start by using 1/2 teaspoon in step #3, then adding more, to taste. In lieu of the vanilla extract, you could add a half vanilla bean, split lengthwise to the butter and sugar in the first step.

6 tablespoons (3oz, 85g) salted butter, cubed
3/4 cup (150g) sugar
1 cup (250ml) heavy cream, warmed
1/2 teaspoon vanilla extract
1 teaspoon flaky sea salt, such as fleur de sel or Maldon, or to taste (see headnote)

Melt butter and sugar together in a large saucepan or pot over medium heat, one that will hold at least 4 quarts (4l), but I recommend one that's larger, if possible.
Continue to cook the sugar and butter together, stirring frequently, until the color is deep golden brown and it starts to smoke. For best results, I cook the mixture until it smells a little smoky, too, but be careful to find the balance between well-browed, and the moment before it's burnt, which is when it's ready to have the cream added. It should be the color of an old copper penny.
Immediately remove from heat and gradually pour in the warm cream, stirring constantly, until smooth. Mix in the vanilla and salt.

Notes

Note: If for some reason the sauce seizes up when you add the cream, you've probably added it too quickly, or it wasn't warm. You can gently warm the sauce over low heat and stir into any bits of caramel are dissolved. If some stubborn bits remain, you can strain them out.

Storage: The sauce can be made up to two weeks in advance and stored in a jar in the refrigerator. It was be rewarmed by placing the jar in a saucepan of warm water, or in a microwave oven.