The main ingredient for making a caramel is sugar. A liquid caramel can be made using any quantity of sugar or water just as long as it follows the ratio of 2 parts sugar: 1 part water.
Simon Hulstone varies the method above by adding double cream instead of water in step 3 to form a salted butter caramel. . If you are adding cream, you could try infusing it first with vanilla as Josh Eggleton instructs in his Caramel panna cotta recipe. Make sure to warm the cream before adding to the hot sugar.