For the crust: Cream the butter, sugar, and salt in the bowl of your mixer until light and fluffy. Add the egg yolk and blend well., Add 1 cup of the graham flour and blend until the mixture smooths out. It will seem quite sandy at first, but will be cohesive in 1 to 2 minutes., Add the milk and the remaining cup of flour. Beat until the mixture forms a moist, firm dough. It will feel very similar to cookie dough., Divide the dough into two equal portions and wrap each in plastic wrap. Chill for at least 2 hours, or up to overnight., Remove one piece of the chilled dough (save the other for another project) and roll on a lightly floured surface to fit a 9" pie pan. Place the dough in the lightly greased pan and bake in a preheated 350°F oven for 8 to 10 minutes, until browned and fragrant. Cool completely before adding the filling., To prepare the filling: Place the cream and fat free half and half in the bowl of a stand mixer fitted with the whisk attachment. Beat until the whisk leaves a trail in the cream., Blend together the sugar and Instant ClearJel in a small bowl. This will prevent clumping when adding to the filling. Add the sugar/Instant ClearJel mixture, one cup of peanut butter, and the Fluff to the cream. Beat until well combined, thick, and fluffy. Little unblended bits of Fluff are fine, even desirable depending on your taste., To assemble: Spread the remaining 1/4 cup of peanut butter in the cooled pie shell. Heap in the fluffy filling, spreading to fill the shell., Loosely cover the pie with plastic wrap and chill for at least 4 hours, or overnight. Serve cold.