Adjust rack to top position (top and middle positions for 4 servings) and preheat oven to 425 degrees. Wash and dry all produce. Halve, peel, and thinly slice onion; mince a few slices until you have 2 TBSP (4 TBSP for 4 servings). Finely chop chives. Dice potatoes into 1/2-inch pieces (peel first for a smoother texture if desired). Trim green beans, if necessary.

Place potatoes in a medium pot with enough salted water to cover by 2 inches. Bring to a boil; cook until tender, 15-20 minutes. Reserve 1/2 cup potato cooking liquid, then drain and return potatoes to pot. Mash with sour cream and 1 TBSP butter (2 TBSP for 4) until smooth, adding splashes of reserved potato cooking liquid as needed. Stir in half the chives, salt, and pepper. Keep covered off heat.

In a medium bowl, combine beef, panko, minced onion, 1 TBSP water (2 TBSP for 4 servings), half the Fry Seasoning (you’ll use the rest later), 1/2 tsp salt (1 tsp for 4) and a pinch of pepper. Form into 10-12 (20-24 for 4) 11/2-inch meatballs.

Place meatballs on one side of a lightly oiled baking sheet. Toss green beans on empty side of same sheet with a drizzle of oil, salt, and pepper. Roast on top rack until meatballs are cooked through and green beans are browned and tender, 14- 16 minutes. (For 4 servings, use 2 baking sheets; roast meatballs on middle rack and green beans on top rack.)

Meanwhile, melt 1 TBSP butter in a large pan over medium-high heat. Add sliced onion; cook, stirring, until softened, 7-9 minutes. Add a drizzle of oil, half the flour (all for 4 servings), and remaining Fry Seasoning; cook, stirring, until lightly browned, 1-2 minutes. Whisk in 3/4 cup water (11/2 cups for 4) and stock concentrate. Bring to a simmer, whisking, until thickened, 2-4 minutes. Reduce heat to low; stir in another 1 TBSP butter.

Season gravy with salt and pepper. Add meatballs and stir to coat. (TIP: Add a splash of water if gravy seems too thick.) Turn off heat. Divide potatoes between plates; top with meatballs and remaining gravy. Add green beans to the side. Garnish with remaining chives and serve.