Lasagne Verdi al Forno

Make pasta: Place a steamer insert into a saucepan and fill with water to just below the bottom of the steamer. Bring water to a boil. Add spinach, cover, and steam until bright green, about 2 minutes. Squeeze spinach to remove excess moisture and process in a food processor to make a paste. Add semolina, eggs, and salt; process until smooth. Transfer mixture to a large bowl and stir in enough flour to make a smooth dough. Knead briefly, then cover with a dish towel and set aside.

Make ragu: In a large skillet, melt butter over medium-high heat. Cook and stir carrot, celery, onion, and bacon in hot butter until onion is translucent. Stir in pork, beef, and ham; cook and stir until crumbly and browned. Stir in beef stock, tomato paste, and oregano. Season with salt and pepper. Reduce heat to low, cover, and simmer for 20 minutes.

While ragu is simmering, make béchamel: Combine butter and flour in a medium saucepan over medium-low heat. Whisk to make a roux. Remove from heat, let rest for 1 minute, then whisk in warm milk. Return to heat and simmer for 10 minutes, stirring constantly, until thickened. Season with salt and nutmeg. Remove from heat.

Cook pasta: Prepare an ice bath. Bring a large pot of lightly salted water to a boil. On a floured surface, divide pasta dough into 3 portions. Roll each portion out to a thin sheet. Cook each pasta sheet in boiling water for 3 minutes; remove and dip in ice water; drain and dry on a clean cloth.

Finish ragu: Stir chicken livers into simmering sauce. Cook for 1 minute, remove from heat, and set aside.

Preheat the oven to 400 degrees F (200 degrees C). Grease a 9x13-inch baking dish.

Assemble lasagna: Place 1 pasta sheet in the bottom of the prepared baking dish. Spread 1/3 of the ragu, 1/4 of the béchamel, 1/3 of the ricotta, and 1/4 of the Parmesan over pasta. Repeat layers twice. Top with remaining béchamel and Parmesan; dot with butter.

Bake in the preheated oven until the top is golden brown, about 30 minutes.