This classic beef and mashed potato casserole is comfort food at its best: a savory ground beef filling, creamy mashed potatoes, and a golden top that makes it perfect for weeknights, meal prep, and feeding a hungry family.
Why You’ll Love This Casserole
- All-in-one dinner with meat, gravy-style sauce, and potatoes
- Great way to use leftover mashed potatoes
- Make-ahead and freezer-friendly
- Kid-friendly flavors with simple pantry ingredients
Ingredients
- 2 lb Yukon Gold or Russet potatoes, peeled and cut into chunks
- 1/2 cup milk (plus more as needed)
- 4 tbsp unsalted butter, divided
- 1 1/2 tsp kosher salt, divided (plus more to taste)
- 1/2 tsp black pepper, plus more to taste
- 1 tbsp olive oil
- 1 1/2 lb ground beef (80/20 or 85/15)
- 1 medium yellow onion, diced
- 2 carrots, peeled and diced (optional but recommended)
- 2 cloves garlic, minced
- 2 tbsp tomato paste
- 2 tbsp all-purpose flour
- 1 1/2 cups beef broth
- 1 tbsp Worcestershire sauce
- 1 tsp dried thyme (or 1 tbsp chopped fresh)
- 1 cup frozen peas
- 1/2 cup shredded cheddar cheese (optional)
How to Make Classic Beef and Mashed Potato Casserole
Preheat your oven to 400°F. Lightly grease a 9×13-inch baking dish.
1) Make the mashed potatoes. Add potatoes to a large pot, cover with cold water, and add 1 tsp salt. Bring to a boil, then simmer 12–15 minutes or until fork-tender. Drain well. Mash with 3 tbsp butter and 1/2 cup milk until smooth and creamy, adding a splash more milk if needed. Season with pepper and salt to taste.
2) Cook the beef filling. Heat olive oil in a large skillet over medium-high heat. Add ground beef and cook until browned, breaking it up with a spoon. If there’s excess grease, drain off most of it.
3) Build flavor. Add onion and carrots and cook 5–7 minutes until softened. Stir in garlic and cook 30 seconds. Add tomato paste and cook 1 minute.
4) Thicken the sauce. Sprinkle flour over the mixture and stir for 1 minute. Slowly pour in beef broth while stirring. Add Worcestershire and thyme. Simmer 3–5 minutes until the filling thickens into a spoon-coating, gravy-like sauce. Stir in peas and taste for salt and pepper.
5) Assemble. Spread the beef filling evenly in the baking dish. Spoon mashed potatoes on top and spread to the edges. Use a fork to create ridges (they brown nicely). Dot with the remaining 1 tbsp butter. If using cheddar, sprinkle it over the top.
6) Bake. Bake 20–25 minutes, or until hot and bubbly with a lightly browned top. For extra browning, broil 1–2 minutes at the end (watch closely).
7) Rest and serve. Let the casserole rest 10 minutes before slicing. Serve with a green salad or steamed green beans.
Tips for the Best Results
- Make the potatoes creamy, not runny: Drain well and mash while hot. Add milk gradually.
- Get a true “casserole slice”: Let it rest after baking so the filling sets up.
- Boost flavor fast: Worcestershire + tomato paste + thyme gives that classic savory depth.
- Don’t skip the fork ridges: More texture = more golden edges.
Easy Variations
- Shepherd’s pie-style: Swap beef for ground lamb.
- Veggie boost: Add diced mushrooms or corn to the filling.
- Cheesy mash top: Mix cheddar into the mashed potatoes, then top with a little more.
- Shortcuts: Use refrigerated mashed potatoes and a bag of frozen mixed veggies.
Make Ahead, Storage, and Freezing
- Make ahead: Assemble up to 24 hours ahead, cover, and refrigerate. Bake covered at 375°F for 25 minutes, then uncover and bake 15–20 minutes more until hot.
- Refrigerate: Store leftovers in an airtight container for up to 4 days.
- Freeze: Wrap tightly and freeze up to 3 months. Thaw overnight in the fridge before baking, or bake from frozen covered until hot through (timing will vary).
- Reheat: Microwave individual servings or warm covered in a 350°F oven until heated through.
Frequently Asked Questions
- Can I use leftover mashed potatoes? Yes. You’ll need about 4 to 5 cups. If they’re stiff, stir in a splash of warm milk to loosen before spreading.
- What’s the best ground beef for this? 85/15 is a great balance. If using 80/20, draining excess fat helps keep the filling from getting greasy.
- Can I make it gluten-free? Yes. Swap flour for a gluten-free all-purpose blend or thicken with a cornstarch slurry (1 tbsp cornstarch mixed with 1 tbsp cold water) added to simmering broth.
