• Preheat oven to 400°F. Line a large, rimmed baking sheet with parchment paper or aluminum foil. Set aside. Spray an 11 x 7-inch casserole pan with cooking spray. Set aside.

for the filling

• Heat olive oil over medium-high heat in a large skillet. When the oil shimmers, add onion and carrot. Cook together for about 8 minutes until they have softened and browned slightly. Add chopped garlic and cook for one minute more. Remove the veg to a bowl and set aside.
• Reduce to medium heat and add the beef, breaking it up as it cooks with a wooden spoon. Create a well in the center of the skillet. Add Worcestershire and tomato paste (or mushroom ketchup) and cook for 3 to 5 minutes, slowly incorporating bits of beef into the paste mixture. Adjust the heat to allow the paste to brown a bit but reducing the heat shy of burning it.
• Add the beef back to the skillet and sprinkle with the flour, the mixed herbs, and season with pepper. Keep the mixture moving in the pan and cook for 2 to 3 minutes to rid the mixture of any flour taste.
• Remove the skillet from the heat and add the red wine. Use the back of the wooden spoon to scrape up any accumulation or fond from the bottom of the skillet. Return to the heat, turning to the gentlest possible simmer, and add the beef broth and 2 bay leaves. Cover the pan and simmer for 30 minutes. After the 30 minute simmer, cut the heat and remove the lid. Allow the filling to cool for 20 minutes before adding it to the prepared baking dish.

for the potato crust

• In a saucepan over low heat, add heavy cream and butter and allow the cream to heat and the butter to melt. Whisk in the herbs and Kosher salt to taste. Keep warm.
• Peel all of the potatoes and cut them into 2-inch chunks. Boil them together or separately in salted water until tender, then drain. I boil mine together and separate them after the boil. The pieces are large enough to where separating them is not hard. Also, it will not matter very much if you end up with some sweet potatoes in the white mash, or some white potatoes in the sweet potato mash.
• Place potatoes respectively into two separate bowls and break them up separately using a hand-held potato masher or a fork. Add half the cream mixture to each bowl and continue to mash to a smooth purée. Add an egg yolk to each and stir to combine well. Optional: if you plan to use an onion cheese and a Double Gloucester cheese in your potato crust, add one cheese to each potato mash (it does not matter which cheese you add to which potato), and mix to combine. Again, this is purely optional, but very, very TASTY!
• Remove the bay leaves from the thick beef mixture. If the mixture appears too thick, add some additional beef broth or stock to thin it out slightly. You should have it at a consistency to where it can be poured into an even layer in an 11 x 7-inch baking pan. Also, to avoid the mash 'sinking' during the bake, cool the filling before loading it up with the mash.
• Starting at one corner, spoon one of the mashed potato mixtures to the opposite corner in as straight a line as you are able and filling in behind it. Repeat the process with the other potato, levelling everything off as you go. If desired, use the tines of a fork to create a pattern on the top of the potato crust.
• Place the casserole dish atop the lined baking sheet and load into the preheated oven. Bake for 15-20 minutes. The savory gravy beneath the potatoes will begin to bubble up along the sides and in the corners, so it's important to place the baker atop a lined tray to catch any drips. At the end of the baking time, turn your oven's broil feature on. DO NOT WALK AWAY! Leave the meat pie beneath the broiler for several minutes allowing the peaks of the potato crust to deeply brown.
• Once the tops of the mash are golden, remove from the oven and let stand 15 minutes before digging in. This delicious Irish dish will be HOT, HOT, HOT! Spoon individual servings into wide, shallow bowls being sure to offer some of each flavor of mash to each person.