In a large bowl combine the softened butter and granulated sugar. This can be done with a handhelf mixer.
Add 4 bananas to a large 4-cup measuring cup. Use a handheld mixer to mash the bananas. Check the volume and add more bananas if needed for a total of 2 cups of mashed bananas.
Add the mashed bananas to the butter-sugar mixture and combine. Add the eggs, vanilla extract, baking soda and salt.
Add the flour and using a large spoon combine by hand. This helps to prevent overmixing.
Divide the batter between the 6 muffin cups in the jumbo muffin pan.
Bake at 350°F for 30 minutes or until a toothpick in the center comes out clean.
Notes
Jumbo Muffin Tin Sizes: Jumbo muffin tins actually come in different depths and diameters. I use a muffin tin where each muffin cup is 2½ inches in diameter at the bottom, 4 inches in diameter at the top, and 1¾ inch in height. In contrast, Nordic Ware sells a muffin tin that is 3 inches in diameter at the bottom, 3.9 at the top, and 1½ inches in height.
These differences will affect the baking time. If you're using a Nordic Ware muffin tin with those dimensions, check your muffins 5-7 minutes before the allotted baking time.
Do Not Overmix: Combining the flour with the wet ingredients with a spoon is one way to help prevent overmixing. If you're using a handheld mixer you may be more likely to overmix the batter, which creates tough muffins.
Amount of Sugar: These muffins are not overly sweet with only ½ cup of granulated sugar. If you prefer a sweeter banana muffin, increase the sugar to ¾ cup.
Brown Sugar: I’ve made lots of banana bread with granulated sugar and brown sugar and there is not much of a difference in flavor. The banana flavor overpowers any difference in granulated vs. brown sugar.
Checking for Doneness: Use a toothpick inserted into the middle of a muffin to check for doneness. It should come out clean when the muffins are done.
The Myth of Brown Bananas: Banana bread rose in popularity during the Great Depression as a way to use up overripe brown bananas so that nothing went to waste! This cultural phenomenon has persisted over time which may be why there’s a general recommendation to use brown overripe bananas.
In reality, those bananas are not sweeter, they just have a stronger banana taste. It is certainly a good way to use bananas that have gone brown, but you do not need to intentionally wait for them to brown before using them. Personally, I find the taste of very brown bananas to be too strong, more akin to banana-flavored candy.