Mix the oil and sugar together. Add the eggs one at a time, beating after each addition.
Sift together the dry ingredients. Add dry ingredients to the wet mix. Fold in the pineapple and the walnuts.
Bake in 3 (8-inch) ring molds ring molds, greased and floured for 35 minutes or 2 (9-inch) greased and floured cake pans for 1 hour. They are done when the center bounces back.
Rum cream: Put the vanilla bean and milk together in a saucepan, and bring to a simmer. Turn off the flame, and allow to steep for 10 minutes. Whisk the egg yolks and sugar in a bowl until sugar dissolves and mixture is a pale yellow. Stir in the hot milk and rum. Return the custard to the pan over low heat, stirring constantly with a wooden spoon until custard thickens slightly. Strain custard through a chinois. Chill over an ice bath to stop the cooking.
Candied ginger: Put the ginger in a small saucepan, and add enough water to cover. Bring the pot to a boil. Drain the water, leaving the ginger and refresh with more cold water. Bring to boil again. Follow this step one more time. After the last time, add the simple syrup to the strained ginger and bring to a simmer. Cook for half an hour. Strain the ginger and spread out on a plate to cool. Save the ginger infused syrup for another dessert.
Assembly: Cut cake into approximately 1-inch slices. Place one slice on a dessert plate and pour a desired amount of rum cream over the slice. Garnish with the candied ginger.