1. Preheat oven to 350. Butter and flour two 9 inch cake pans.
2. Sift flour, baking powder and salt.
3. Beat butter until fluffy. Gradually add sugar and beat two minutes more. Add eggs, beating well. Beat in rum and vanilla.
4. Combine sour cream and baking soda. Add bananas to sour cream mixture and stir until well blended.
5. Add dry ingredients to butter mixture alternately with banana mixture, beginning and ending with dry ingredients. Stir in chopped peanut butter bars.
6. Divide batter between prepared pans. Bake about 30 minutes, until center of cake feels firm and tester in center comes out clean. Cool 10 minutes. Remove from pans. Cool completely.
7. Combine cream (or sweetened condensed milk), butter, powdered sugar, chocolate chips and corn syrup over low heat or in microwave. Stir until butter and chips melt. Add rum and vanilla.
8. Pour into a small container, cover and refrigerate about 2 hours, stirring occasionally. Put between layers and frost sides and top. Cover top and sides (which I never can) with chopped peanut butter bars.