1Add olive oil to a hot pan. Add mince, spread it out, turn heat up high, and let the meat sear for about 5 minutes. Once a crust has developed, mix and break it up. Keep on high heat and sear until moisture evaporates.
2Add tomato purée, bay leaves, salt, and garlic. Sauté on medium-high heat for 5 minutes. Then add onions, celery, carrots, chilli flakes, and herbs. Close the lid and reduce heat to medium.
3Let this cook for 15-20 minutes, or until onions are soft and translucent.
4Add cumin, coriander, and chilli powder. Cook the spices for about 5 minutes, sautéing on medium heat.
5Add tinned tomatoes and passata, and one can of water. Close the lid and simmer on low heat for 1-2 hours, stirring every 20 minutes.
6For the béchamel: Melt butter, then add flour and cook for 3-4 minutes, stirring constantly. Reduce heat, add one cup of milk and whisk until smooth. Repeat with another cup, then add remaining milk.
7Increase heat to medium and whisk constantly until thick. Do not overcook, as it will thicken further in the oven. Season with salt, pepper, and a pinch of nutmeg (optional).
8Assemble lasagna and bake in a preheated oven at 180°C for 20-25 minutes uncovered if using fresh lasagna sheets, or bake for 25 minutes with foil and 10-15 minutes without if using dry sheets.