If giving these cakes as gifts, use disposable aluminum foil loaf pans and give the cakes in the pans.
Cakes: Heat oven to 350 degrees F. Grease and flour four 8 x 3 3/4-inch loaf pans.
Split open vanilla bean and scrape seeds into cream. Drop pod into cream and heat until scalding. Let cool.
Whisk together the eggs, sugar and salt until well blended. Sift the flour and baking powder together. Whisk the sifted dry ingredients into the egg/sugar mixture just until blended. Remove (and discard) the vanilla bean pod from the cream, and whisk cream into the batter. Gently mix in the melted butter, pour batter into the prepared loaf pans and bake for 50 to 60 minutes or until golden brown and a cake tester comes out clean. While cake is baking, prepare Syrup.
Syrup: Combine sugar, water and corn syrup in a heavy saucepan. Stir mixture over medium-high heat until it comes to a simmer. Continue to heat WITHOUT FURTHER STIRRING until mixture comes to a full boil. Cover and continue to boil for about 1 minute or until all sugar is dissolved and liquid is clear. Remove from heat and let cool for about 5 minutes.
Stir in liqueur.
When you remove cakes from the oven, allow them to cool for about 5 minutes.
Run a knife around the edges of the pan and turn cakes out of pan. Immediately return cakes to the pan. Use a thin wooden skewer to poke numerous holes into the cakes, about 1 inch apart. The holes should go all the way from the top to the bottom of the cake. Pour 1/4 syrup mixture over each cake and, if desired, sprinkle with toppings*. Let cool until the cakes have absorbed the syrup. Remove from pans.
*Liqueurs and Optional Toppings
Amaretto and 1/3 cup toasted almonds
Grand Marnier and 2 tablespoons grated orange zest
Frangelico and 1/3 cup chopped toasted hazelnuts
Rum and brandy (while not really liqueurs) work well in these cakes, also.