This is lovely served on any pasta. I think it originally came from an old WW Pasta Cookbook, so it's fairly low in calories and it's so simple that even my boyfriend cooks it. It makes quite a 'dry' pasta sauce.
Heat the oil in a pan and fry the onion on a gentle heat until soft but not browned.
Add the thyme, garlic (if using) and spinach.
Continue to cook on low heat until the spinach leaves have wilted, approximately 2-3 minutes. If you're spinach was very wet and there is a lot of water in the pan, drain some off otherwise the sauce will be very runny. If you're not sure drain it into a separate bowl you can always add some later if you feel it's too thick.
Add the ricotta cheese and mix, using a wooden spoon, until it forms a smooth sauce.
Season, using nutmeg (I use more than stated above, but then I really like nutmeg), salt, freshly ground pepper and powdered vegetable stock to taste.
Sprinkle with toasted pine nuts and serve straight away on your favourite pasta.