Take note, if you like a deep, dark molassasy taste in your butterscotch, use dark brown sugar. If not, use light brown sugar. I, myself, use a combination. I like this dessert with ¾ cup of light brown sugar and ¼ cup rich moscavado sugar.
Heat the oven to 325°F. Lay a kitchen towel at the bottom of a large roasting pan and line up 8 (4 to 6-ounce) ramekins with a little space between them. Set aside until you’re ready to fill.
If you think of it the night before, mix the cream and milk and put the vanilla bean pod and the scraped seeds into the mix to let them sleep together all night. When you’re about to make the pots de crème, put the milk, cream & vanilla mixture on low, gentle heat and let them have a last hurrah to extract the deepest vanilla flavor. Make sure you don’t go past a quick scald. Just let them get a little warm and snuggly.
Beat egg yolks until smooth, and have at the ready.
In a large, heavy bottomed saucepan, heat the butter, brown sugar, scotch, and salt until the sugar is melted and the mixture goes from a grainy mass to something liquid and languid and the spoon trails through the pan like it’s rubbing over velvet. This will take about 5 minutes and you’ll know you’re getting close when the room suddenly smells distinctly like caramel.
Turn the heat down a bit and add the milk mixture in a slow, steady stream. It might bubble and seize up a bit, but just keep the heat going until the caramel melts and turns the milk a soft amber color. Take it just to the point of boiling, then turn down the heat.
Now you have to temper by taking a bit of the liquid, maybe 1/3 of it, and whisking it into the egg yolks very slowly. When this meeting goes well, you can introduce the rest by whisking it in a steady stream until everything kind of comes together. Strain into a large measuring cup or something else that has a spout, discarding the vanilla bean (or dry it out and scent a cup of sugar with it). Put a teakettle of water on to simmer, then carefully pour the custard into the prepared ramekins. When the teakettle is simmering, pour the water into the roasting pan, careful not to splash any into your custard pots. This water bath should fill the pan enough to cover the ramekins at the half mark. Cover with foil and bake at 325°F for about 40 minutes. Check for doneness often starting at 30 minutes because doneness will largely depend on what type of ramekin you use and you want these little pots to stay silky and smooth. You’ll take them out when they are just set and still jiggle a bit in the center. Let them cool at room temperature in the water bath for about an hour or two. You can serve at room temperature, or store in the fridge uncovered until they’re fully cooled down. These little pots are wonderful served cold at the end of a warm summer evening. Top with unsweetened crème fraîche and a little flaky salt. For a little more flourish, you could also serve with deep chocolate madeleines.