In a large mixing bowl, combine flour, sugar, salt and baking powder. Add in butter using the beater blade of an electric mixer until it resembles coarse crumbs.
Add egg, bananas, and buttermilk. Combine completely. Fold in chopped walnuts.
On a large baking sheet with parchment paper or silpat, drop dough. Using floured hands (or sprinkling a little extra flour on the top of the dough) pat into a large 10inch circle.
Using a large knife or pizza cutter, slice dough into 8-10 large triangles. Separate slightly.
Bake in a 350 degree oven for 25 minutes. Remove from oven and make sure scones are completely separated. Bake an additional 10-15 minutes. Remove and cool completely.
For the frosting, beat cream cheese with powdered sugar and heavy cream. Beat for 3-5 minutes until desired consistency. Spread over scones and immediately sprinkle with chopped walnuts. Serve and enjoy.
Store in airtight container for up to three days in refrigerator.