Begin with the crust so that it has time to chill.
Mix the salt and flour.
Add the shortening.
Using a pastry cutter, combine the ingredients until the mixture resembles small crumbles.
Scramble the egg in the buttermilk.
Add the milk and egg mixture to the dough.
Stir to distribute.
Form a dough ball.
Wrap in plastic wrap and chill of a minimum of one hour.
Begin the filling.
Sauté the sweet onion, garlic, and chopped tomatoes in the olive oil on medium heat until the onion and tomatoes are softened.
Add the broth, the tomato paste, the green onions, and the parley, and stir to distribute.
Cook until it reaches a slow boil.
Continue on a slow boil until the tomatoes are significantly softened.
Add salt and pepper to taste.
In a small plastic container with a lid, mix the flour and enough water to create a thickening agent with the consistency of a thick, creamy gravy.
Reduce the heat to medium-low and add the thickening agent slowly and in stages, stirring thoroughly between.
Stop adding thickening agent when the mixture is noticeably thicker but is still smooth enough not to harden.
Remove from heat.
Add the juice of 1/2 lime and stir to distribute evenly.
Allow the mixture to cool to room temperature.
Cut the heart of palm into 1/4 inch slices, then do a coarse cross chop. Do not make the pieces too small.
Cut the shrimp in half by volume (the tail portion a little longer than the torso portion).
Set the shrimp and heart of palm aside.
Retrieve the chilled dough out of the fridge, cut a 2/3 portion, wrap the remaining 1/3 portion and return it to the fridge.
Using plastic wrap sheets in a cross pattern over top and bottom, roll the first dough portion to standard pie dough thickness.
Peel the top layer of plastic wrap off, center over a 9-inch spring form cake pan, and gently push the rolled crust into the pan, lining the bottom and sides fully.
Peel off the remaining layer of plastic wrap.
Mix the cut shrimp and heart of palm into the cooled filling mixture and pour all into the spring form pan over the bottom crust.
Roll out the remaining 1/3 of crust between the same crosses of plastic wrap.
Place over the filling.
Trim excess crust.
Press the top edges together to seal.
Brush the crust with the yolk egg wash.
Make several small venting holes with a toothpick.
Place on a cookie sheet or cover the oven rack with tin foil.
Bake at 375° F for 40-45 minutes or until the crust is a golden brown.
Remove from oven and place on cooling rack.
Allow to cool for about 15 minutes.
Use a knife to ensure that the crust is not attached to the top of the spring form pan, then gently open the spring latch.
Slice and serve. The pie should still be pretty hot.