In a small bowl mix the creme fraiche with a pinch of sea salt, a pinch of white pepper and a pinch of nutmeg. Taste and adjust the seasoning.
Heat up a large frying pan and add a tiny bit of olive oil.
Put the onions in until they start to soften but don't let them colour. Remove the onions and set aside to cool.
Now add another tiny dribble of oil to the pan and cook the bacon just to remove any moisture, don't let it colour as once in the hot oven it will end up looking burnt.
Remove and set aside to cool.
Lay a sheet of greaseproof paper on a baking sheet and pop the pastry (about 35cmx22cm) on top.
Spread the crème fraiche mixture over the pastry leaving a 1cm edge.
Cut the Chavroux into 5mm slices and dot evenly spaced on top.
Sprinkle over the onions followed by the bacon. Lightly brush the edge of the pastry with a little oil.
Put onto the middle shelf of your oven and cook for about 12 minutes.
