Preheat the oven to 355°F. Line 4 or 6 muffin cups with paper liners.
Place peeled banana in a medium bowl and mash it well with a fork. Add butter, egg, vanilla seeds, and sugar, and mix well with a hand mixer, around 2-3 minutes. Place a fine-mesh strainer over the bowl and add flour and baking soda to the strainer. Sift dry ingredients into the wet and mix again, until the batter is sticky and has no lumps.
Stir in the chocolate chips and mix until just combined.
Spoon the mixture evenly into the paper liners and bake for 20 minutes or until a toothpick comes out clean and the muffins are golden brown in color. Cool on a wire rack for 15 minutes, then serve.
Notes
Tip: These muffins freeze beautifully! Place them in an airtight container or freezer bag and keep frozen for up to 3 months.