Preheat oven to 350 degrees F. and line 12 muffin cups with liners (foil is preferred)
Place butter into a small skillet over medium heat.
Cook, let bubble and swirl pan until the butter has turned golden brown. Transfer to a heatproof bowl and let cool for 5 minutes.
Pour butter into a large mixing bowl. Add sugar, bananas, and vanilla mixing to combine.
Add eggs, stirring to combine.
Stir in flour, baking soda and salt then stir in blueberries.
Fill prepared muffin cups 3/4 full and bake for 23-25 minutes, until baked through.
Remove and let cool for 5 minutes if drizzling with icing.
To prepare icing, place powdered sugar and heavy cream into a medium bowl.
Whisk until desired icing consistency. Drizzle over warm muffins if desired.