Preheat your oven to 350°F (175°C).
Grease your 9x5-inch loaf pan with butter or line it with parchment paper.
In a mixing bowl, beat the unsalted butter and granulated sugar together until light and fluffy.
Beat in the eggs, one at a time, ensuring each is fully incorporated.
Add the mashed bananas and vanilla extract to the mixture and stir until well combined.
In a separate bowl, whisk together the all-purpose flour, whole wheat flour, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring gently just until combined.
Gently fold in the chopped Snickers bars.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula.
Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean.
Allow to cool in the pan for about 10 minutes, then transfer to a cooling rack to cool completely.