Shepherd's pie is pure comfort food with an English passport. This casserole of ground beef with veggies - like carrot, peas, and onion - with a baked topping of mashed potatoes has everything you could want in one dish. When you've got a hungry crowd to feed, this is a classic that delivers.
Peel and cut potatoes into a 1" dice. Bring a medium pot with potatoes covered by lightly salted water to a boil. Reduce to a simmer and cook until tender, 16-18 minutes. While potatoes cook, prepare ingredients. Peel and halve onions. Cut halves into ¼” dice. Peel, trim, and cut carrot into ¼" dice.
Make the Mashed Potatoes
When potatoes are fork tender, drain in colander and return to pot. Add butter and half the cream and mash with a potato masher or fork until smooth. If needed, add additional cream, 1 Tbsp at a time, to achieve desired consistency. Season to taste with 1 tsp. salt and a pinch of pepper.
Start the Filling
Heat 1 tsp. olive oil in a large oven-safe pan over medium-high heat. Add carrots and onions and cook, stirring occasionally, until tender and onions are translucent, 6-8 minutes. Add ground beef to pan and break into small pieces. Cook until almost no pink remains, 6-8 minutes.
Finish the Filling
When beef is nearly cooked and almost no pink remains, add miso paste to pan. Sprinkle flour over beef mixture and stir until fully incorporated. Add demi-glace and ½ cup water and mix until demi-glace is dissolved. Bring to a simmer and add peas. Simmer until ¼ cup liquid remains in pan, 4-5 minutes. Remove from burner and season with 1 tsp. salt and ¼ tsp. pepper.
Bake the Shepherd's Pie
If pan used for filling is not oven safe, transfer filling to casserole dish prepared with cooking spray. Spread mashed potatoes into even layer over filling, leaving a 1" margin around edge. Use a fork to "rake" surface of potatoes. Grooves will help potatoes brown. Top potatoes with Parmesan cheese. Place pan or casserole on prepared baking sheet and broil until potatoes begin to brown, 4-6 minutes. Carefully remove from oven.
Plate the Dish
Scoop a serving of shepherd's pie into a shallow bowl or plate and dig in!