Slice the brussels sprouts into thin discs using a mandolin.
Preheat the oven to fan-assisted 180C / 200C / 400F / gas 6.
Lay the puff pastry sheet on the non-stick baking tray and score a 1cm border round the edge taking care not to cut all the way through. Feel free to make a pattern on the border if you have time.
Spread on the caramelized red onion chutney before toping with the brie.
Bake for 15 mins, then remove from the oven before topping with the shredded brussels sprouts, and returning the tart to the oven for a further 5-7 mins until the pasty is puffed round the edges and golden.
Serve with pomegranate seeds and extra shredded brussels sprouts (if you like some crunch on top).