Step 1

Melt the butter in a heavy-duty saucepan and add the brown sugar and salt over medium heat. Cook, stirring once or twice until the sugar has melted, is very bubbly and has turned slightly darker. It will also begin to smell of caramel. Remove from the heat and pour into a pan lined with a baking mat or parchment. Allow the butterscotch to cool completely then break into small pieces using a mallet or the bottom of a heavy pan.

Step 2

In a large measuring cup or bowl combine the butterscotch, rum and vodka. Cover tighty with plastic wrap and allow to sit until the butterscotch as dissolved, stirring occasionally, about 24 hours.

Step 3

Refrigerate the mixture until very cold, about two hours. Place a coffee filter inside of a large funnel, and pour the liquid into the funnel not letting the liquid come up above the top of the coffee filter. Place a piece of plastic wrap over the top of the funnel and down the sides to prevent the alcohol from evaporating. Keep the funnel draining liquid in the refrigerator. You will need to add more of the mixture as it drains until all the clear liquid has drained from the filter and the butter scum and solids remain in the filter. Cover in an air-tight container until serving.