Preheat oven to 425 degrees. Wash and dry all produce. Halve, peel, and mince shallot. Mince or grate 1 garlic clove (2 cloves for 4 servings). Place peppercorns in a zip-close bag and crush with a rolling pin or bottom of a pan. Dice potatoes into 1/2-inch pieces; place in a medium pot with remaining garlic, a large pinch of salt, and enough water to cover by 2 inches. Boil until tender, about 15 minutes.

In a large bowl, soak bread with 2 TBSP water (4 TBSP for 4 servings). Let sit until liquid has absorbed, then break up with your hands or a spatula until pasty. Add beef, 1/2 tsp thyme (1 tsp for 4), half the shallot, minced garlic, salt, and pepper. Combine and form into two 1-inch-tall loaves. Place on one half of an oiled baking sheet. Bake on top rack for 10 minutes. (If making for 4, make 4 loaves and bake until cooked through, 22-25 minutes.)

In a medium bowl, combine green beans with a large drizzle of olive oil, salt, and pepper. Once meatloaves have baked for 10 minutes, remove from oven and place green beans on opposite side of baking sheet. (For 4 servings, roast on a separate sheet.) Roast until beans are tender and meatloaves are fully cooked, 12-15 minutes.

Once potatoes are tender, scoop out 1/4 cup cooking water (1/2 cup for 4 servings), then drain. Return potatoes and garlic to pot. Mash with half the sour cream and 2 TBSP butter (4 TBSP for 4), adding reserved cooking water as needed, until smooth. Season with salt and pepper to taste. Cover pot to keep warm.

Heat a large drizzle of olive oil in a medium pan over medium-high heat. Add remaining shallot. Cook, stirring occasionally, until slightly softened, about 30 seconds. Add 1/4 cup water (1/2 cup for 4 servings), stock concentrate, and 1/2 tsp peppercorns (1 tsp for 4). Cook until thickened, about 1 minute. Turn off heat. Stir in remaining sour cream and 1 TBSP butter (2 TBSP for 4). Season with salt and pepper (to taste).

Divide potatoes and green beans between plates. Top with meatloaves and sauce.