Put the pastry into a tart tin. Use a fork to make holes in it. Then spread the mustard.
Cut the apples in little dices, then cook them in butter for 15 minutes or so. When they start to melt, take out of the heat.
Put the apples on top of the mustard, then sprinkle with the crushed nuts.
Cut the Camembert into slices, then arrange it on the tart.
Bake 25 minutes at 360°F (180°C).
There you are, you Camembert tart is ready !