Preparation

• Heat the oil in a large pan. Add the onion and garlic and cook for 5 minutes until softened.
  Add the marinara and balsamic vinegar and simmer for 20 minutes, until thickened.
  2 Meanwhile, heat a large pan over a medium heat. Wash the spinach, then add to the pan and wilt. Place in a sieve over a bowl to get rid of excess water then, once cooled, pat dry with paper towel and roughly chop. Add to the ricotta with a pinch of freshly-grated nutmeg and season to taste.
  3 Place a generous teaspoon of the ricotta mixture on a slice of lasagne sheet and spread evenly.
  Roll up the rotolo, using the tea towel to help. Start off with your hands to get a nice tight roll, then lift up the towel from the bottom and roll the pasta all the way up into a tight log
  Wrap the log up tightly in the tea towel and use string to tie each end. Cook the rotolo in a large pan of salted boiling water for 15 minutes.
  
  Carefully remove the tea towel then slice the rotolo into 6–8 even slices.
  Once the tomato sauce has thickened to a good consistency, stir through most of the basil, reserving some to garnish. Pour he sauce into the base of a roughly 21 x 21 cm (9-inch square) baking dish and place the lasagne roll-ups in the dish, so they are stood up. Bake for 25-30 minutes, until lightly golden. Garnish with the remaining basil and serve.