2. Toss butter in flour and combine using your favorite pie dough method. Pulse in a food processor, rub with fingers or use a pastry cutter.
Sprinkle in water a little at a time until a shaggy dough is formed. Wrap.
Let chill for at least one hour or overnight.
Preheat oven to 425F.
1. Melt butter in a 9-inch saute pan over medium-high heat.
2. Halve bananas lengthwise. Place flat side down in butter and sear until starting to caramelize.
3. Meanwhile dust a flat surface with flour. Roll whole wheat pie dough out to a 13" diameter circle.
4. Add brown sugar to the butter and whisk to dissolve. Add rum. Optionally, you can use the flame of the burner to burn off the alcohol, but it will burn off whether or not you see the flame. If the mixture looks broken, add cream.
Add salt. Pour liquid over bananas. You may not use all of it! Working quickly, fold the edges of the dough around the center, leaving an open ring in the middle.
Whisk egg with a little water(1-2 tbsp). Brush the dough with egg wash onto the dough and sprinkle with sugar, if desired.
Bake at 425F for 15 minutes or until golden brown. Wait until cool and then cut into 8 pieces.