Step 1

Put the cup of water and granulated sugar in a heavy-bottomed saucepan.

Step 2

Bring to a boil, stirring a couple of times to make sure all the sugar dissolves.

Step 3

Allow the mixture to boil for just a few seconds, and then remove it from the heat.

Step 4

Leave the syrup in the pan and keep it convenient to the stove.

Step 5

In a heavy-bottomed saucepan that is taller than you think you'll need, combine the dark brown sugar, the ounce of water, butter, and salt.

Step 6

Stir a couple of times, and then put the lid on the pan.

Step 7

Heat over medium heat until all the butter has melted and the sugar is dissolved.

Step 8

Remove the lid and cook the mixture together until it reaches 300-310F on an instant-read thermometer.

Step 9

Carefully pour about half the simple syrup into the butterscotch, stirring well. Mixture will bubble up a Very Lot, and the butterscotch may harden.

Step 10

Once the bubbling has calmed down, add the rest of the simple syrup and whisk over low heat until the butterscotch is completely melted.

Step 11

Whisk in the vanilla off the heat.

Step 12

Allow the syrup to cool and then store in an airtight container in the fridge for up to 2 weeks.

Step 13

Warm the syrup before serving and then stir well to incorporate any butter that is floating on top.