Set your oven to 350°F (175°C). Grease a 9x5-inch loaf pan or line it with parchment paper.
In a bowl, whisk together flour, baking soda, and salt. Set aside.
In a large bowl, mash ripe bananas. Add peanut butter, melted butter, both sugars, eggs, and vanilla. Mix until smooth and creamy.
Slowly add the dry mix, alternating with the milk. Stir gently until just combined—don’t overmix.
Fold in chopped Reese’s and Reese’s Pieces (optional) until evenly distributed.
Pour batter into the prepared pan and smooth the top. Bake for 55–65 minutes, or until a toothpick comes out clean.
Let it sit in the pan for 10 minutes, then transfer to a wire rack to cool completely.
Melt ¼ cup peanut butter and drizzle over the cooled loaf before serving.