Preheat oven to 350°F and prepare loaf pans by greasing only the bottoms to allow proper rising.

In a medium bowl, mash 3 to 4 very ripe bananas with a fork or potato masher until smooth, yielding 1 1/2 cups.

In a large bowl, beat sugar and softened butter with an electric mixer until fluffy; then add eggs and beat until smooth and thoroughly blended.

Add the mashed bananas, buttermilk, and vanilla to the sugar mixture and beat until smooth.

Using a spatula or spoon, gently stir in flour, baking soda, and salt just until moistened, accepting some lumps and flour streaks.

Gently fold in chopped nuts, if desired, then pour the batter evenly into the prepared loaf pan(s).

Bake 8-inch loaves for about 1 hour, or a 9-inch loaf for about 1 hour and 15 minutes, until a toothpick inserted in the center comes out clean; cool in the pan(s) on a cooling rack for 10 minutes.

Using a dinner knife, loosen the edges of the loaf from the pan, then carefully invert and tap to release onto an oven mitt-protected hand; place top-side up on a cooling rack to cool completely for about 2 hours before slicing.

Serve with softened butter, if desired; tightly wrap completely cooled bread and store at room temperature for up to 4 days, or refrigerate for up to a week.