Using a hand mixer or a stand mixer with the beater attachments, beat the butter and white sugar until light and fluffy. Add in the eggs, one at a time, beating thoroughly after each. Mix in the bananas.
Whisk together the dry ingredients, then bet into the banana mixture until thoroughly combined.
Pour into the prepared pan, spread evenly throughout the pan.
Warm up the 1/1 cup of REESE Spreads slightly, then pour over the top of the cake. Use a spoon or knife to swirl through the top and about 1/4 of the way into the batter.
Bake for 35-40 minutes, or until a knife inserted into the middle comes out clean (note: you are looking to see if the cake is cooked ,not the chocolate spread, so if you see banana cake that sticks to the knife it's not done. Chocolate that sticks to the knife is ok!)