Step 1

In a deep saucepan (at least 2 quarts--no smaller, because the mixture bubbles up!), add the sugar and water. Whisk to combine.

Step 2

Turn the heat to medium-high and let the sugar melt and dissolve without stirring. If you see sugar crystals on the sides of the pan, use a pastry brush dipped in water to gently push them back in the pan. Do not stir.

Step 3

Once the sugar is dissolved, crank the heat to high and watch it turn an amber color. Watch it closely, it happens quickly! You can swirl the pan gently to evenly brown the caramel.

Step 4

Meanwhile, heat the heavy cream until it's steaming, and small bubbles are forming around the edges.

Step 5

Turn off the heat to the sugar mixture, and add the heavy cream all at once. Be careful--it bubbles up triple the size! It is very hot!

Step 6

Next, whisk in the butter, salt and vanilla. Whisk until smooth.

Step 7

Pour the mixture into a jar to cool and use as you like.