for sauce: Can be made a day ahead.
In a medium saucepan, bring half and half to a simmer. Scrape in seeds from vanilla bean; add bean. In a medium bowl, whisk sugar and egg yolks. Gradually whisk in half and half mixture. Return mixture to saucepan; stir with a wooden spoon over medium heat for about 5 minutes, until custard thickens and leaves path on back of spoon when finger is drawn across (do not boil). Strain sauce. Cover and chill until cold.
Preheat oven to 400 degrees.
Butter two 1-quart soufflé dishes. Sprinkle the bottom and sides of dishes with sugar; shake out excess. Place dishes on a baking sheet.
Melt butter in a heavy medium saucepan over medium heat. Add flour. Stir until mixture is smooth and bubbly, about 2 minutes. Gradually whisk in milk. Bring to boil while whisking continuously. Boil until thick, about 1 minute. Remove form heat. Stir in sugar, molasses, rum, ginger, vanilla extract, cinnamon, and salt. Cool until just warm, about 10 minutes. (can be prepared two hours ahead. Cover with plastic wrap, and let stand at room temperature. Whisk over low heat until warm before continuing). Mix in egg yolks.
Using an electric mixer, beat egg whites with cream of tartar in a large bowl until stiff but not dry. Fold beaten egg whites into the yolk mixture.
Divide mixture among prepared dishes. Bake until soufflés are puffed and golden, about 20-25 minutes. Serve immediately with sauce.