Heat oven to 450 degrees F with the rack in the center. Using a food processor, pulse all the dry ingredients together. Add the butter and shortening, then pulse until it resembles course chopped nuts. Add the buttermilk, truffles and Parmesan, then pulse again until it forms moist clumps.
Dump the wet dough onto a well floured surface. Flour your hands and press the dough into an even rectangle 1 1/4-inch high. Use a 2-inch cutter to cut the biscuits. Gather the scraps, press and cut again--you should have 12 biscuits all together. (Try to cut as many in the first round as possible. The second batch will be slightly tougher.)
Using the melted butter or egg wash, brush the top of each biscuits and place them on a parchment paper lined cookie sheet. Lightly sprinkle them with salt and bake for 10-12 minutes.
While the biscuits are warm, crack them open and smear them with pesto. Then layer a piece of prosciutto on each biscuit and place the top back on.