Preheat oven to 350 degrees. Line two 8" x 5" loaf pans with parchment paper. Helpful tip: secure paper to edges of pan with binder clips. This prevents paper from sliding when batter is added to pan. Set pans aside.
In mixing bowl, combine mashed bananas with oil, eggs, sugar, vanilla and lemon juice. Mix until all ingredients are well combined.
In another bowl, whisk together the dry ingredients; flour, baking powder, baking soda and salt. Gradually add the dry ingredients to the wet ingredients, using a large whisk to combine. Stir the batter until just combine and until there are no more lumps.
With a rubber scraper, fold in 3/4 cup of the chocolate chunks, reserving the remaining 1/4 cup for topping the loaves. If using chopped nuts add these in as well.
Evenly divide the batter into the two prepared pans.
Remove the binder clips from the edges of the pans (if you were using to secure the parchment paper) and place loaves in oven. Bake at 350 degrees for 45-50 minutes or until a toothpick inserted comes out clean and crumb free.
Let the loaves cool 10-15 minutes before slicing.