Pre-heat oven to 190ºC , place a flat oven tray on the centre shelf to heat. Line a 32cm x 12cm rectangular or 23 cm round flan tin with the pastry sheets, cutting and trimming to fit neatly. Chill until required.
In a medium frying pan heat oil and sauté onion and garlic for 2-3 minutes until softened but not brown. Add spinach leaves and cook a further 2 minutes until wilted and bright green, drain off any excess liquid.
Whisk eggs with mascarpone and sour cream and season well.
Spread the spinach mixture over the base of the pastry lined tin, and then carefully pour over the mascarpone egg mix.
Sprinkle with pine nuts and place tart on the pre-heated tray, bake for 15-20 minutes until pastry is golden then reduce heat to 180ºC and cook a further 10-15 minutes until the filling is set and golden.
Cool for 10 minutes in the tin before removing to serve.
Serve with summer salad greens, vine tomatoes, red onion and an extra dollop of mascarpone with a drizzle of sweet chilli sauce. Sprinkle with a few toasted pine nuts to finish. Serves 6.