Melt sugar over medium high heat in a medium sauce pan, swirling the pan often until the sugar has all melted and it begins to turn an amber color.
Add the butter, whisking vigorously until all the butter has melted.
Take the pan off the heat and slowly pour the Baileys Irish Cream in, whisking vigorously until incorporated. Quickly add the fine sea salt and whisk until it is incorporated.
Dip a spoon into the caramel and wipe it along the inside of a glass, spreading the caramel all over until the whole inside of the glass is covered. You can also dip the rim of the glass into the caramel. Set aside.
Let the caramel sit for 15 minutes before transferring it to an airtight container. Store in the fridge (I use a mason jar).