Place spinach into boiling water until wilted, drain well and squeeze out any excess liquid.
In a large bowl combine ricotta, onion and parsley.
Arrange 3 sheets of lasagne on the base of an ovenproof pan (approx. 33cm x 23cm). Top with 1/3 each of pumpkin, tomato sauce and spinach ricotta mixture. Repeat twice and top with remaining lasagne sheets.
To make topping, break eggs into flour and mix until smooth. Slowly add milk to flour mixture while whisking, pour into a saucepan and bring to the boil, continue whisking until smooth and thickened. Add pepper and ground nutmeg, pour over top of lasagne and sprinkle with cheese.