boil the lasagne sheets until soften, around 4 minutes. set aside. make sure they do not stick together.
sauté the spinach: put olive oil, garlic, chili in pan, cook slowly until garlic caramelized. add spinach, stir until well mix with oil. cover with lid for around 2 minutes. turn off the burner and set aside.
to prepare the pasta rolls: place flat the lasagne sheet. trim it until the width of it could just fit in the baking dish. brush it with a thin layer of pesto. place the spinach evenly on the sheet, add gruyere, parmesan and half of the mozzarella ball. mozzarella should be torn into small pieces when placing. pinch of salt and pepper. roll up the lasagne sheet with toppings into around 1.5" cannelloni roll. repeat for the rest four sheets.
the sauce: put olive oil, garlic, chili in pan. cook with slow heat until garlic turns golden. add the tomato puree. stir until well mix with the ingredients. finish with drizzles of balsamic vinegar to bring out the flavor of the sauce.