Beef & Potato Au Gratin Dinner

Ingredients

Beef Base

• 1.5 lbs (680 g) lean ground beef (85/15 or 90/10)
• 1 medium yellow onion, finely diced
• 4 cloves fresh garlic, minced
• 1 tbsp Worcestershire sauce
• 1 tsp dried thyme (or 1 tbsp fresh thyme leaves)
• 1 tsp smoked paprika
• 1 tsp kosher salt
• ½ tsp freshly cracked black pepper
• 1 tbsp olive oil (optional, if using extra-lean beef)

Potato Layers

• 2.5 lbs (1.1 kg) Yukon Gold potatoes (about 5–6 medium), scrubbed and sliced thin (⅛-inch / 3 mm thickness)
• ½ tsp kosher salt (for sprinkling between layers)

Garlic & Herb Cheese Sauce (Mornay)

• 3 tbsp (45 g) unsalted butter
• 3 tbsp (25 g) all-purpose flour
• 2 cups (480 ml) whole milk, warmed
• 1 cup (240 ml) low-sodium beef broth (or heavy cream for extra richness)
• ¼ tsp ground nutmeg
• ½ tsp onion powder
• 1 tsp Dijon mustard
• 1 cup (100 g) sharp cheddar cheese, freshly shredded
• 1 cup (100 g) Gruyère or Swiss cheese, freshly shredded

Crispy Cheese Topping

• ½ cup (50 g) sharp cheddar cheese, shredded
• ½ cup (50 g) Gruyère cheese, shredded
• 2 tbsp fresh chives or flat-leaf parsley, finely chopped (for garnish)

Instructions

1. Prep the Oven and Pan

1. Preheat your oven to 375°F (190°C) with the rack positioned in the center. Grease a deep 9×13-inch (3-quart) baking dish or an oven-safe 12-inch cast-iron skillet with non-stick cooking spray or softened butter.

2. Brown and Season the Beef

1. Place a large skillet over medium-high heat . Add the ground beef and diced onion.
2. Cook for 6 to 8 minutes, breaking up the meat with a wooden spoon until fully browned and the onions are translucent.
3. Drain excess grease, leaving about 1 tablespoon in the pan for flavor.
4. Stir in minced garlic, Worcestershire sauce, smoked paprika, dried thyme, 1 teaspoon salt, and ½ teaspoon black pepper. Cook over medium heat for an additional 1 to 2 minutes until aromatic.
5. Remove from heat and spread the beef mixture evenly across the bottom of your prepared baking dish.

3. Slice the Potatoes

1. Slice the Yukon Golds into uniform ⅛-inch rounds using a mandoline or a sharp chef’s knife. Do not rinse the slices after cutting; the surface starches help bind and thicken the sauce during baking.

4. Build the Cheese Sauce (Mornay)

1. In a medium saucepan, melt 3 tablespoons of butter over medium heat .
2. Whisk in 3 tablespoons of flour. Cook, stirring constantly, for 1 to 2 minutes until lightly golden and nutty (a pale blond roux).
3. Gradually pour in the warm whole milk and beef broth in a steady stream, whisking vigorously to prevent lumps.
4. Bring the liquid to a gentle simmer over medium heat , stirring frequently until it thickens enough to coat the back of a spoon (about 4 to 5 minutes).
5. Reduce heat to low . Whisk in Dijon mustard, onion powder, and ground nutmeg.
6. Remove pan from heat. Add 1 cup shredded cheddar and 1 cup Gruyère in small handfuls, stirring smoothly until fully melted. Season to taste with a pinch of salt and pepper.

5. Assemble the Gratin

1. Arrange half of the sliced potatoes in an overlapping, shingled layer directly over the ground beef base.
2. Lightly dust with ¼ teaspoon salt, then ladle half of the warm cheese sauce evenly over the potatoes.
3. Layer the remaining sliced potatoes over the top, finish with the remaining ¼ teaspoon salt, and pour the rest of the cheese sauce over everything. Use a spatula to gently press down so the liquid seeps into the crevices.
4. Sprinkle the reserved 1 cup of mixed cheese (cheddar and Gruyère) across the top.

6. Bake to Tender Perfection

1. Lightly spray a sheet of aluminum foil with cooking oil (to keep the cheese from sticking) and tent it tightly over the baking dish.
2. Bake covered at 375°F (190°C) for 45 minutes .
3. Carefully remove the foil. Return to the oven uncovered for an additional 15 to 20 minutes , until the potatoes pierce easily with a fork and the edges bubble vigorously.
4. (Optional browning) Switch the oven to Broil (High) for 2 to 3 minutes, watching closely until the cheese develops golden-brown blistered spots.

7. Rest and Serve

1. Remove from the oven and let rest on a wire rack for 12 to 15 minutes . This rest period is essential; it allows the sauce to settle and thicken so portions cut cleanly rather than running. Garnish with chopped fresh chives before slicing.

Nutrition

Calories: 565 kcal — · Protein: 37 g 74% · Fat: 31 g 40% · Carbohydrates: 35 g 13% Dietary · Saturated Fat: 16 g 80% · Fiber: 3.5 g 12% · Sugar: 5 g — · Sodium: 780 mg 34%