Directions

1. In a large bowl, whisk eggs until blended. Whisk in milk, cream, 1/2 cup sugar, vanilla seeds, salt, and rum. Add bread; toss to combine. Let soak until most of the liquid has been absorbed, 45 minutes to 1 hour, occasionally pushing bread down into egg mixture.
2. Meanwhile, set out a 9-inch round baking pan thats 2 inches deep. In a medium saucepan over high heat, combine remaining cup sugar, vinegar, and 1/2 cup water; stir until sugar has dissolved. Cook, without stirring, until sugar is dark amber, 7 to 10 minutes. Remove pan from heat; carefully add 1/4 cup water (mixture will sputter), and swirl pan until caramel is smooth.
3. Working quickly, pour caramel into baking pan, carefully tilting pan back and forth so caramel coats bottom and some of the sides; set aside until caramel is firm, about 10 minutes.
4. Preheat oven to 350 degrees; set a kettle of water to boil. Butter uncoated interior of baking pan; spoon in bread mixture, packing tightly to fit. Cover with a round of parchment paper.
5. Place baking pan in a roasting pan; pour enough boiling water in roasting pan to come halfway up the sides of baking pan. Bake 1 1/4 hours, or until a knife inserted in the center of bread pudding comes out barely clean (do not overbake). Remove parchment; let stand 5 minutes. Run a metal spatula around the edge; invert bread pudding onto a large rimmed serving plate. Serve at room temperature.