Beef Shepherd’s Pie

Place potatoes in a large pot with enough salted water to cover by 2 inches. Bring to a boil and cook until tender, 12-15 minutes. Turn off heat, drain, and return potatoes to pot along with 3 TBSP butter (6 TBSP for 8 servings).

While potatoes cook, heat a drizzle of oil in a second large, heavy-bottomed pot over medium-high heat. Add onion, carrots, celery, and garlic; cook, stirring occasionally, until beginning to soften, 3-4 minutes. Add beef, half the rosemary, half the thyme, and a pinch of pepper (all the rosemary and all the thyme for 8 servings). Cook, breaking up meat into pieces, until browned and cooked through, 4-6 minutes. Carefully drain any excess grease from pot.

Add tomato paste and 2 TBSP flour (4 TBSP for 8 servings) to same pot; stir to coat. Add peas, stock concentrates, and 1 cup water (1¾ cups for 8); stir to combine. Cook, stirring occasionally, until thickened, 2-3 minutes. Stir in half the parsley and half the chives. Taste and season with salt if needed. Carefully transfer mixture to an 8-by-8-inch baking dish (use a 9-by-13-inch baking dish for 8).

Add cheese, sour cream, ¼ cup milk, and one egg yolk (½ cup milk and two egg yolks for 8 servings) to pot with potatoes; mash until smooth. (Discard egg white or save for another use.) Season generously with salt and pepper.