Heat a large, heavy based saucepan over medium heat. Add olive oil, onion, carrots, celery, garlic and oregano and sauté for 10 minutes.
Add beef mince and sausage, break up with a wooden spoon and cook until browned.
Add remaining ingredients and bring to the boil. Cover and simmer for 2 hours, stirring occasionally and adding a little water if required.
For bechamel, melt butter in a medium saucepan, add flour, stir to mix through and cook until sandy in colour and texture.
Gradually pour in the milk, whisking continuously until smooth, and cook until thickened.
Remove from the heat and whisk in nutmeg and cheese.
Preheat oven to 180°C. Bring a full kettle to the boil, place spinach into a large bowl and pour over the boiling water. Allow to stand for a minute, drain, cool down in running water, then squeeze out excess water through a cheesecloth.
Place a little ragu into the base of a 36x25x8cm lasagna dish, followed by a layer of lasagna sheets.
Spread 3 cups of ragu on top of the pasta and drizzle with béchamel. Continue for five more layers, adding a layer of spinach in the second and fourth layer.
Top the lasagna with cheese and bake for 25-30 minutes.
Allow to rest for 15 minutes before portioning and serving. Sprinkle with chopped parsley.
