For the pots de creme: Preheat the oven to 280 degrees F. In a medium pot set over high heat, scald the cream and milk; the mixture should be just about to boil, then remove from the heat. Whisk the sugar and yolks in a bowl until light and frothy, 1 minute. Temper the yolks by pouring some of the hot cream over the yolks slowly and whisking vigorously. Then pour the yolk mixture into the cream and do not return to the stovetop. Add the rum, vanilla and chocolate, and whisk slowly until the chocolate melts and is completely incorporated. Pour the mixture into six 6-ounce ramekins and bake in a water bath until the creme is set, about 1 hour.
Cool in the refrigerator until cold, overnight.
For the butterscotch: Melt the butter in a medium saucepan and set over medium-high heat. Add the brown sugar and stir to dissolve. Cook until the sugar thickens and reaches the soft-ball stage, a candy thermometer will read 235 degrees F, the sugar will just start to darken in color. Whisk the cream and salt in slowly, being careful as the cream will steam and the sugar mixture may clump. Keep whisking and cooking until smooth. Remove from the heat and add enough food coloring to make the sauce bloody!
Serve the pots de creme drizzled with some of the bloody butterscotch.