Preheat oven to 350°.
Cream butter and sugar.
Mash bananas, beat eggs and add to the bananas with vanilla and buttermilk; mix well and add to creamed butter and sugar.
Sift together flour, soda and salt.
Add to banana mixture, beat well.
Pour into 2 greased and floured 9x5x3-inch loaf pans.
Bake 45 to 50 minutes or until bread pulls away from sides of pan. Cool.
(Note: start checking with toothpick after 35 minutes -- you don't want the bread to overbake.)
To prepare topping: Melt butter in saucepan.
Add sugar and milk.
Cook until very syrupy.
Remove from heat and add chopped nuts.
Pour over bread spreading to all the corners
and place under broiler until bubbly and brown. Watch closely.