The Pastry: Mise en place (is a French culinary phrase which means "putting in place" or "gather". It refers to the setup required before cooking): Make sure your butter is all cubed up and it's sitting in the fridge, herbs are already chopped, if you're using them and you have a cup or bowl of ice water on hand. In a large bowl, mix the flour and salt and herbs together with a whisk, if you are using the herbs.
Add the butter cubes to the mixture and mix quickly with your fingers, remember the heat of your fingers and hand will warm the butter up very fast, which is why you want to mix quickly until the mixture resembles sand and small pebbles, only tiny beads should remain.
Add the ice water, up to 14 tblsp at first then add, one at a time a tblsp of the ice water until the dough holds together when you squeeze by your hand. You may not need all the ice water.
Create a rounded oval shape which is not too thick, cover in plastic wrap and place in the refrigerator until needed. I don't like making the dough a ball as when it comes straight out of the fridge will take longer to get it flat with a rolling pin. You want the dough to be very cold when rolling but it will also crack on the edges more so when cold which is why I recommend a much flatter pile of dough. Your finished product should be that you can see small tiny patches of butter interwoven in your pie dough top and bottom.

The Filling: Using either boneless skinless thighs or chicken breasts, sprinkle salt, pepper and granulated garlic on both sides and grill (ideally) or use a heavy bottoms pan and heat up some vegetable oil and pan fry each side until done, really thick breasts can be butterflied open for more even and quicker cooking. Cube up the chicken and set aside. Keep the cubes the same size as the vegetable cubes.
Cut the carrots into cubed pieces and boil in water for 2-3 minutes, until the are cooked through but not too soft, set aside.
Blanch the peas in hot water just until any frozenness disappear, drain and set aside.
You can skin the potatoes or don't for a more rustic look. Cube up the potatoes and cook in boiling water until cooked 3/4 of the way, about 4 minutes depending on how large you made the cubes, drain and set aside.

The Stock: Using home made stock is best (See my Chicken Stock recipe). Next best thing is making your stock with Better Than Bouillon Chicken Bouillon or the Roasted Chicken Bouillon (I think they also make a low sodium chicken bouillon). If your using the Bouillon method, it's easiest to mix all three tblsp with as little warm or hot water as you can and once you integrate the Bouillon making sure it's dissolved, add more water until you get to 11 cups. Once you have the mixture, chicken stock, you can add a tsp of salt and 1 tsp of fine ground black pepper. If your not using the herbs in the dough, you should add a tsp thyme to the stock now. Bring to a simmer over medium/low heat, stir, once hot taste for slat and pepper content and adjust accordingly. Get your corn starch slurry together by measuring our ¾ cup of corn starch and adding just enough cold water until it can be stirred, mix well, once the stock is simmering and your happy that it tastes chickeny and is seasoned well, add some hot stock into your "slurry" until you can pour easily pour the mixed slurry back into the stock, but first turn down the heat to stop the simmering and stirring simultaneously as the stock meets with the slurry and will react by thickening your chicken stock, once you've added three quarters of your slurry, turn the heat back to a simmer, this is when the magic happens, stir the chicken stock it should be getting thicker, now adjust the stock with more slurry until you have a very thick base for your chicken pot pie.
Stir in all the vegetables and the chicken, taste! Adjust the seasoning if necessary. Let cool, as it cools it will thicken even more. You can stop at this point and make the pot pies the next day if you wish.

Putting it all together: Pre-heat the oven to 400° F. Take the dough from the refrigerator and using a rolling pin roll out the dough between ⅛ to ¼
If you like a bottom crust: form a sheet onto a pie plate or baking dish pushing the sheet to conform to the inner curves of the pie plate or baking dish and trim off the excess dough that overhangs the edges using a butter knife. Add the pot pie filling into the pastry lined baking apparatus very close to the top leaving a ¼ of space. Add a top pastry sheet over your fillings and using a knife slice an X into the center of the pie to allow steam to escape. If your making a huge 13x8 baking dish you can cut three X's into the top to help the steam escape. Line a baking sheet with foil and place the pie on it, place in the center of the oven for 20-30 minutes or until the insides are bubbling hot and the crust id golden. You may need to check at 15 minutes to make sure the edges are not browning too much, if they are take a couple of strips of foil and wrap around the crusts edges.
If you like a only a top crust: fill the baking dish with pot pie filling and leave a ¼ inch gap to the top. Add a sheet of pastry dough over the top and using a butter knife trim the edges off, place on a foil lined baking sheet and bake for 30-30 minutes. Be aware that the edges can burn, check at 15 minutes and use some foil strips to cover the edges if it happens.

You can also par bake a top crust by measuring how large the top needs to be to fit on your baking pan, bowl or whatever you are using. Cut it to size and place on a baking sheet and bake at 350 degrees until tan in color, not golden. Then use these pre cooked tops to put over your bowl of hot pot pie filling you heated on the stove top and then only bake for 5 minutes until the pie top heats up and gets a more golden color, 10 minutes tops. Remember if you forget to cut an X into the pre-baked tops, if the filling bubbles over it will all be over the sides of the crust!

Boil the carrot cubes until just about tender as they'll finish cooking in the completed pie. Drain and set aside.

In hot very hot skillet, add 1 tblsp high heat oil like vegetable, canola or peanut oil. Add half the lamb and sear on 2 sides then remove to a small bowl. Repeat the other half of lamb cubes.

Once the lamb is seared and set aside, as well as your carrots and peas, get a large sauce pot filled with water on the stove on high heat, add in the potato cubes and bring to a boil, in about 10 minutes the potatoes will be fork tender, check at the 8, 10, 12 minute mark so you don't end up with potato mush! Once they are fork tender, drain off the water completely and then put the potatoes back into the pot, add the 4 tblsp unsalted butter, ¾ of the cream or milk, the ½ tsp ground black pepper and 2 tsp of salt to start with. Mash the potatoes with butter and stuff, until they seem fairly smooth and smashed, remove the smasher and use a large spoon to stir it all togather adding more cream or milk if they are too stiff. Taste for salt content and add more if needed. Set potatoes aside.

Pre-heat your oven to 400°F.

In the same pan as you seared the lamb, heat up the lamb stock or whatever stock you are using. Add the 1 tsp of Tony's Chachere's Creole spice, garlic powder and 1/2 tsp black pepper and bring to a simmer. Now add the lamb cubes and juice from the lamb. Bring the stock back up to a fast simmer for 15-20 minutes or until the lamb is as tender as you like, in the last 5 minutes add the carrots and peas to the lamb and stock.

Now in a small bowl or cup mix the cornstarch with about 6-8 tsps of the hot stock only (no peas or lamb!). Once your cornstarch slurry is mixed well, turn the heat down to low and mix in ¾ of the slurry quickly into the lab, peas and stock and bring the mixture to a simmer. Keep stirring at this point, after 20-30 seconds the cornstarch slurry should have thickened up the stock, if you think it needs to thicken more add the rest of the slurry in, stirring quickly as you add it. You should now have a great gravy based lamb and vegetables for the bottom portion of your shepherd's pie.

Let's put it all together, in a 9 x 9" pan, add the lamb/gravy/vegi mix first. Making sure its evenly distributed, now add the mashed potatoes a small scoop at a time, first at the corners, then the center, then fill in the bare spots, grap a spatula and lightly smooth the potatoes over the entire top so you can't see any gravy/lamb mix. I then dragged a fork lightly over the top to give the top of the potatoes a chance to crisp up even more in the oven. Lastly add the tsp of butter to the center of the pie and place in your pre-heated oven at 400°F. for 20-25 minutes. I then moved it to my broiler for about 1-2 minutes to get that golden brown rows from raking the top with the fork! Remember, if you are bringing it out of the fridge, let it sit out at room temperature for 20 minutes before putting in the oven.