I would use creme fraiche instead of double cream.
I make a caramelised red onion and goats cheese Tarte Tatin:-
Saute red onions, when translucent add brown sugar and allow to caramelise.
Tip the onion into a quiche dish, season and top with sliced/chopped goats cheese.
Roll puff pastry and cover the onion and cheese mixture. Bake for about 30 mins in a moderate oven.
Allow to cool slightly, run a knife around the edge then invert the tart onto a serving dish. Top with sprigs of thyme.
Happy cooking