Boil the potatoes for the topping: Peel the potatoes and lower into 1-inch chunks. Position in a medium saucepan. Upload sufficient cool water to hide the potatoes via 1 inch. Quilt the pot and convey to boil over excessive warmth. As quickly because the water is boiling, discover, then scale back the warmth to a simmer. Prepare dinner, adjusting the warmth as had to deal with a gradual, stable simmer, till potatoes are fork delicate, about 12 to 16 mins. Drain the potatoes and go back them to the saucepan. If the potatoes are very wet, warmth the saucepan over low, shaking it infrequently, till any liquid at the floor of the potatoes has cooked off, about 1 minute, then take away from the warmth.

Combine the topping in combination: With a potato masher or picket spoon, mash the potatoes neatly. Scatter the butter items excessive. Upload the Parmesan, salt, and pepper.

With a picket spoon or rubber spatula, stir a couple of occasions, till the butter is most commonly melted.

In a small bowl or liquid measuring cup with a spout, whisk in combination the milk and egg yolk.

Upload to the potatoes. Stir to mix. The potatoes will have to be wealthy and fluffy.

Make the filling: Coat a 9×9, 8×10, or 11×7 casserole dish with nonstick spray. Position rack within the middle of your oven and preheat to 400℉. In a big skillet, warmth the oil over medium-high warmth. As soon as it’s scorching and shimmering, upload the onion and cook dinner till it’s starting to brown, about 3 mins.

Upload the garlic and tomato paste. Stirring often, cook dinner 30 seconds.

Upload the meat (or lamb), salt, and pepper. Prepare dinner, breaking aside the beef, till it’s browned and cooked via, about 4 mins. If there’s extra grease within the pan, moderately drain it off (this will have to no longer be an issue in case your pork is round 93% lean).

Sprinkle the flour excessive, and cook dinner, stirring often, for 1 minute.

Stir within the broth, Worcestershire, thyme, and bay leaf. With a rubber spatula or picket spoon, scrape the ground of the pan to take away any stuck-on browned bits. Convey the liquid to a boil, scale back the warmth to low, then quilt the pan and let simmer gently till the sauce thickens quite, about 10 mins. Take away the thyme and bay leaf. Style and modify the seasoning as desired.

Stir within the peas and carrots.

Switch the beef aggregate to the ready dish, spreading it into a fair layer.

Upload the mashed potatoes via spoonfuls excessive, beginning across the edges to create a “seal” (this may save you the filling from effervescent up). With a spatula, gently unfold the potatoes into a fair layer.

Line a rimmed baking sheet with a work of parchment paper, then position the dish on best (this may catch any portions of the filling that bubble over). Bake the shepherd’s pie exposed at the middle rack for 25 mins, or till the potatoes start to brown. Let cool for no less than 10 mins previous to serving.