Preheat the oven to 350 degrees.
Using a hand mixer or a stand mixer fitted with the paddle attachment, cream shortening and sugar for 1-2 minutes or until fluffy. Scrape down the bowl once complete.
Add in eggs one at a time, beating well after each addition.
Add mashed bananas and vanilla extract. Mix until combined. Scrape down the bowl once complete.
In a separate bowl, whisk together dry ingredients (flour, baking soda, salt).
Add dry ingredients to wet ingredients, mix until combined.
Scoop one cup of batter into a separate bowl.
Melt chocolate chips and add to the one cup of reserved batter. Stir until combined.
Thoroughly grease a 9x5x3 inch loaf pan.
Alternate spooning chocolate batter and original batter into loaf pan.
Once both batters have been completely spooned into the loaf pan, run a butter knife through the batter 3-4 times to create swirls.
Add 4-5 heaping spoonfuls of peanut butter down the middle of the loaf pan, lightly pressing each one down with your fingertips.
Bake for 45 minutes to 1 hour, or until toothpick comes out clean.
Let rest for at least 10 minutes, then turn the loaf out of the pan to serve.