Bulgogi Beef Lasagna

Steps

1. 1

   Chill and slice beef

   • Place the trimmed steak on a plate in the freezer for 15 minutes, until the outside is firm but the center still gives slightly when pressed.
   • Using a sharp knife, slice the steak across the grain as thinly as you can, about ⅛ inch (3 mm).
   • Stack a few slices at a time and cut them into ½-inch (1 cm) pieces.
   • Transfer to a large mixing bowl.

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   Ready when: Slices are thin enough to bend easily and pieces are about ½ inch (1 cm)

   Tip: Don't freeze the beef solid. Partially frozen is the goal, and a rock-hard center will crush the knife's edge and tear the meat.

2. 2

   Marinate the beef

   • Add the soy sauce, brown sugar, grated pear with its juice, garlic, ginger, sesame oil, gochujang (if using), and black pepper to the beef.
   • Stir well with your hands or a spoon so each piece is coated.
   • Cover and refrigerate for 30 minutes (up to 4 hours).
   • The grated pear contains an enzyme that tenderizes the meat, so don't marinate beyond 4 hours.

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   Ready when: Beef is evenly coated and sitting in a loose, dark marinade

3. 3

   Boil the noodles

   • While the beef marinates, bring a large pot of water (about 5 quarts / 4.7 L) to a boil.
   • Add the 1 tablespoon salt and the noodles.
   • Cook, stirring occasionally in the first minute so they don't stick, for about 8 minutes, or 1 to 2 minutes less than the package says.
   • Drain, rinse briefly with cool water, then lay the noodles flat in a single layer on a lightly oiled baking sheet or a clean counter so they don't stick together.

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   Ready when: Noodles are flexible and bend without breaking but are still slightly firm in the center (they finish cooking in the oven)

   Tip: Underdone noodles are the goal. Fully soft noodles turn mushy after 50 minutes of baking.

4. 4

   Sear the bulgogi

   • Heat 1 tablespoon of the neutral oil in a 12-inch (30 cm) skillet over medium-high heat.
   • Add the sliced onion and cook, stirring occasionally, for 4 minutes until softened and lightly browned at the edges.
   • Transfer to a plate.
   • Return the skillet to high heat with the remaining 1 tablespoon oil.
   • Using a slotted spoon, lift the beef out of the marinade (reserve the liquid in the bowl) and sear it in 3 batches, spreading it in a single layer and leaving it undisturbed for 1 minute, then stirring for 1 to 2 minutes more.
   • Return all the beef and onion to the skillet, pour in the reserved marinade, and simmer for 3 to 4 minutes, stirring, until the liquid reduces to a thick, glossy glaze that barely pools.
   • Stir in 3 of the sliced scallions and remove from heat.

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   Ready when: Beef is browned with no pink remaining and the sauce coats the meat like a glaze, with almost no loose liquid in the pan

   Tip: Crowding the pan steams the beef instead of searing it. Work in batches, and make sure the sauce is reduced, because a wet filling makes soupy lasagna.

5. 5

   Make the béchamel

   • Melt the 4 tablespoons butter in a 3-quart (2.8 L) saucepan over medium heat.
   • Whisk in the flour and cook, whisking constantly, for 2 minutes until it smells lightly nutty and looks like wet sand but has not browned.
   • Pour in about 1 cup (240 ml) of the warm milk while whisking vigorously until a thick, smooth paste forms.
   • Gradually whisk in the remaining milk.
   • Cook, whisking often and scraping the corners, for 6 to 8 minutes until the sauce comes to a gentle bubble and coats the back of a spoon.
   • Whisk in the ¾ teaspoon salt and the white pepper.

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   Ready when: Sauce is smooth, thick enough to coat a spoon, and a finger drawn across the spoon leaves a clean line

   Tip: Add the first cup of milk slowly while whisking. Dumping it in all at once causes lumps. If lumps do form, whisk hard or pour through a sieve.

6. 6

   Assemble the layersOven 375°F / 190°C

   • Preheat the oven to 375°F (190°C) with a rack in the center.
   • Grease a 9×13-inch (23×33 cm) baking dish with the softened dish butter.
   • Spread 3/4 cup (180 ml) béchamel over the bottom.
   • Arrange 3 noodles side by side across the dish, trimming to fit if needed.
   • Spread one-third of the beef (about 1 heaping cup) over the noodles, drizzle with 1 cup (240 ml) béchamel, and sprinkle with one-quarter of the mozzarella (about 85 g).
   • Repeat to make a second layer of 3 noodles, one-third of the beef, 1 cup béchamel, and another quarter of the cheese.
   • For the final layer, add the last 3 noodles, the remaining beef, and the remaining béchamel (about 1¼ cups / 300 ml), then top with the remaining half of the mozzarella (170 g).
   • Grease one side of a large sheet of foil with a little butter and cover the dish, buttered side down.

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   Ready when: Dish is filled with three even layers and a smooth, fully covered top

   Tip: Spread the béchamel all the way to the corners and edges so no noodles are left bare, because exposed noodles turn hard and dry.

7. 7

   Bake coveredOven 375°F / 190°C

   • Place the dish on a rimmed baking sheet to catch drips and bake, covered, at 375°F (190°C) for 30 minutes, until the edges are bubbling and the lasagna is heated through.

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   Ready when: Béchamel is bubbling around the edges of the dish

8. 8

   Uncover and brownOven 375°F / 190°C

   • Remove the foil carefully, away from your face, since the steam is hot.
   • Return the lasagna to the oven and bake, uncovered, at 375°F (190°C) for 20 minutes more, until the top is golden brown in spots and bubbling.
   • Check that the center registers 165°F (74°C) on an instant-read thermometer.
   • If the top isn't browned, broil on high for 1 to 2 minutes, watching closely.

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   Ready when: Top is golden with browned spots, edges are bubbling, and the center reads 165°F (74°C)

   Tip: Broiler time is short: cheese goes from golden to burnt in under a minute.

9. 9

   Rest and garnish

   • Let the lasagna rest on a wire rack for 15 minutes so the béchamel sets and the layers hold together when cut.
   • Sprinkle with the remaining 5 sliced scallions and the toasted sesame seeds.
   • Cut into 8 squares with a sharp knife and serve with a spatula.

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   Ready when: Bubbling has stopped and the edges are set enough to cut clean squares

   Tip: Cutting too early causes the layers to slump and the sauce to run out.