Preheat oven to 200°C (180°C fan-forced). Unroll defrosted pastry sheet, using a 12cm round pastry cutter (or small saucer), cut 8 circles. You may need to re-roll the trim to get the 8th.
Line the tart tins pastry followed by baking paper, fill each one with baking weights, bake for 20 minutes, remove from oven, scoop out the weights and return to oven for a further 5 minutes.
Meanwhile, heat the olive oil in a medium sized saucepan over medium heat, add the onion and garlic sauté until onion is translucent, about 5 minutes, add thyme leaves and baby spinach, pop a lid on the pan and cook for 1 minute or until spinach just wilted, remove from heat and transfer to a bowl. Using the same pan lightly sauté bacon pieces until just cooked. Combine the bacon with onion and spinach mixture.
In a medium sized mixing bowl, lightly whisk the eggs, then add crème fraiche, salt, pepper and the cheese, whisking until combined. Divide the onion, bacon and spinach between the tarts, pour in the crème fraiche mixture and sprinkle with the parmesan. Bake in the preheated oven for 15 minutes or until just set.