Heat the condensed milk caramel, butter and 8 tbsp of water in a pan and bring to a simmer. Stir until the caramel dissolves. Add the salt and the rum (if using), mix, then leave to cool slightly.

"Rich butter rum flavors meet espresso, white chocolate sauce, and steamed milk, topped with a caramel drizzle for a velvety, toasty delight." I don't know about you, but that sounds so delightful.