Prep your pan and oven. Heat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with a parchment sling for easy removal.

Mash the bananas. In a large bowl, mash the bananas with a fork until mostly smooth with a few small lumps. You should have about 1 and 1/4 to 1 and 1/2 cups.

Whisk wet ingredients. Add peanut butter, oil, brown sugar, eggs, and vanilla to the bananas. Whisk until smooth and glossy. If the peanut butter is very thick, warm it slightly so it blends easily.

Combine dry ingredients. In a separate bowl, whisk flour, baking soda, baking powder, salt, and cinnamon.

Bring it together. Add the dry mixture to the wet mixture. Stir gently with a spatula until almost combined. If the batter looks very thick, fold in 2–3 tablespoons milk to loosen it.

Add mix-ins (optional). Fold in 1/2 to 3/4 cup chocolate chips, chopped peanuts, or a mix of both. Don’t overmix.

Fill the pan. Spread the batter evenly in the prepared loaf pan. For a nice finish, sprinkle a few chocolate chips or chopped peanuts on top, or slice a banana lengthwise and press gently on the surface.

Bake. Bake for 50–65 minutes, depending on your oven. Start checking at 50 minutes. The loaf is done when a tester comes out with a few moist crumbs and the top springs back lightly.

Cool properly. Let the bread cool in the pan for 15 minutes, then lift it out and cool on a rack for at least 1 hour before slicing. This helps the crumb set and keeps slices from crumbling.

Serve. Slice and enjoy plain, warmed with a pat of butter, or toasted with extra peanut butter and a drizzle of honey.