Prepare the mirepoix and garlic paste

• Peel the celery to remove the fibrous strings, then slice it finely.
• Finely dice the onion and set out the shredded carrots.
• Sprinkle the garlic with salt and smash it into a paste.

Sweat the vegetables

• Heat a generous drizzle of olive oil in a Dutch oven over medium heat.
• Add the onion, celery and carrots and cook until soft and sweaty.
• Season generously with salt, then stir in the garlic paste.

Brown the tomato paste and beef

• Add the tomato paste and cook until nicely browned and deep in flavor.
• Add the ground beef with a touch more salt and break it up.
• Season with smoked paprika and chipotle chili powder and brown the meat.

Build and simmer the meat sauce

• Pour in the beef stock and scrape up the browned bits from the pan.
• Once bubbling, add the San Marzano tomatoes and crush them into the sauce.
• Taste and adjust the seasoning, bring to a boil, then cover and simmer on low.

Make the béchamel

• Melt the butter in a saucepan over low heat, then whisk in an equal amount of flour.
• Cook for a couple of minutes to remove the raw flour taste.
• Whisk in the milk in several batches until silky smooth, then season with salt and black pepper.

Finish the béchamel with cheese

• Stir in the mozzarella, then add parmesan until the consistency feels right.
• The sauce should coat the back of a spoon and hold when you swipe it.
• Loosen with more milk if too thick, or add parmesan if too watery.

Cook the lasagna sheets

• Bring well-salted water to a rigorous boil and add the lasagna sheets.
• Cook for 8 to 10 minutes, stirring a couple of times so they don't stick.
• Drain the sheets.

Layer the lasagna

• Start with a layer of meat sauce, then a layer of lasagna sheets, trimming them to fit.
• Add more meat sauce, a layer of béchamel and a quick layer of mozzarella.
• Repeat the process once more, without drenching it in béchamel.

Bake the lasagna

• Bake at 190 °C for about 30 minutes.
• Switch to broil for the last 5 minutes to brown the top.

Rest and serve

• Let the lasagna rest for at least 20 to 30 minutes before slicing.