Divide Chorizo mince in 8 pieces and roll each piece to form a ball. Heat 1 tablespoon of the oil in a heavy-based ovenproof saucepan over medium heat. Add the chorizo and cook, stirring occasionally, for 5 minutes or until just golden. Add the garlic and ½ cup of the oregano and cook for a further 1–2 minutes or until golden. Add the tomato, purée, sugar, salt and pepper and bring to the boil. Cook for 8–10 minutes or until just reduced.
Transfer the mixture to a large bowl and set aside. Place the ricotta and pecorino in a large bowl and mix to combine. Set aside.
Preheat oven to 180°C (350°F). Line the base of the saucepan with 1 layer of lasagne sheets, trimming to fit. Top with 2 cups of the chorizo mixture and another layer of lasagne sheets. Spoon over half the ricotta mixture and spread evenly. Top with another layer of lasagne sheets, spoon over remaining ricotta mixture and spread evenly.
Sprinkle with the mozzarella, top with remaining chorizo mixture and cook for 25 minutes. Combine the remaining oil with the remaining oregano leaves, sprinkle over the top of the lasagne and cook for a further 5 minutes or until golden. Serves 6–8.