Lay down about 6 feet (1.8 meters) of tinfoil on a flat surface. Place place 4 clusters of 2 lasagna noodles towards the left half of the foil sheet, leaving about a ½-inch (1 cm) gap in between each cluster.
2. Step
Fold the right half of foil over the noodles, pressing flat. To help you see where the noodles are, run your finger along the edges of the noodles to create a rough outline in the foil.
3. Step
Fold the top and bottom flaps of foil over, creasing and pressing flat.
4. Step
Flip the foil sheet onto the table so that it’s now standing, then arrange into a square box, using the 4 groups of noodles as a visual guide. Fold and crease over any excess foil to join the ends together, then set aside.
5. Step
In a large pot, melt the butter over medium heat.
6. Step
Whisk in the flour, cooking until the mixture reaches a light golden color.
7. Step
Slowly drizzle in the milk and bring to a boil, whisking constantly until smooth. Mix in salt, pepper, and nutmeg. Bring to a boil.
8. Step
Transfer the béchamel to a large bowl and press plastic wrap onto the surface of the sauce to prevent a skin from forming. Set aside.
9. Step
Heat oil in a very large pot over high heat. Once the oil begins to shimmer, add the onions, carrots, and celery and cook until the vegetables have started to sweat but aren’t browning.
10. Step
Add in the ground beef and use a wooden spoon or spatula to break up the meat into small pieces.
11. Step
Cook the beef, stirring occasionally, until half of the liquid has evaporated.
12. Step
Add in the tomato sauce, tomato paste, chicken stock, salt, and pepper, stirring to combine evenly and breaking up any last lumps.
13. Step
Turn down the heat to low, and simmer, covered, for about 2 hours.
14. Step
Preheat oven to 350°F (180°C).
15. Step
To assemble, line a greased 9x9-inch (23x23-cm) square baking pan with 2 sheets of foil that extend over the sides.
16. Step
Spread a thin layer of béchamel on the lined baking pan and top with 2 lasagna noodles. Spread a thin layer of meat sauce evenly across the noodles, followed by a thin layer of béchamel. Repeat the layering process, following the order of: 2 noodles, meat sauce, and béchamel. Alternate the direction of the lasagna sheets after every layer.
17. Step
After 50 layers, place the foil box over the lasagna, helping it stay upright and stable.
18. Step
Continue with the layering process until the 99th layer.
19. Step
Sprinkle Parmesan on top, then cover the whole lasagna with foil.
20. Step
Bake for about 1½ hours, uncovering the foil halfway, until the top is a deep golden brown.
21. Step
Cool for at least 2 hours, then carefully lift out the lasagna with the foil sleeves onto a large cutting board.
22. Step
Peel away the foil walls, then sprinkle the top of the lasagna generously with chives.
