Bake pie shell according to package (empty); cool and set aside.
Melt butter in saute pan, add banana slices and cook for a minute to two minutes (do not over cook or the bananas will cook down) on low heat.
Add brown sugar, vanilla and cinnamon, stirring for two minutes (this avoids cooking down of bananas).
Turn off heat, add rum and walnuts. Stir and cool. (It will thicken as it cools).
In a medium sauce pan over medium heat, combine half and half, six tbsp of measured sugar and salt. Bring to simmer, stirring occassionally (till sugar is disolved). Keep on heat while making the yolk mixture.
In a small bowl, whisk egg yolk together till smooth. Add remaining sugar and whisk till combined.
In another small bowl, whisk together cornstarch and a little water till fully blended.
Add cornstarch to yolk mixture, whisking till fully blended.
Take half and half mixture and pour ribbon slowly (just a little) into yolk mixture whisking fast (too much and fast could cook the eggs!).
Pour yolk mixture into the half and half mixture and continue to cook over medium heat.
Whisk constantly until mixture is thickened and glossy.
Remove from heat and stir in butter slices and vanilla extract until fully blended.
Strain cream in fine mesh strainer into a medium bowl-push all throughly and may do it twice to remove any lumps.
Cover top in plastic wrap (prevents from skin-forming) and cool.
Pour Banana Foster's into cooled pastry shell.
Next, spread pastry cream over the Banana Fosters.
Place plastic wrap on pastry cream top and chill.
When ready to serve, remove plastic wrap and decorate, garnish with whipped topping/whipped cream, sprinkles,. chopped nuts, dried banana chips, if like.