To make the crust: cut butter into cubes and freeze, along with the shortening. In the meantime, pulse the flour and salt together. Add frozen butter and shortening until slightly incorporated. Drizzle in vinegar and ice water and dump onto a floored surface. Knead for a minute until it all comes together and wrap in a disc. Rest for at least an hour.

Once the dough is rested, preheat oven to 350F and roll dough onto floored surface. Place inside pie dish, crimping edges. Make filling.

To make filling, melt the butter until brown and nutty, about 5-8 minutes. Let cool and whisk into eggs, sugar, flour, buttermilk, and salt. Pour filling into unbaked pie crust and sprinkle with vanilla bean powder. Bake for about 40-50 minutes, until middle is set. Refrigerate and serve cold.