Bring 1 litre of salted water to the boil. Cut a 3mm deep cross into the base of the Brussels sprouts and add to saucepan. Cook for 3-4 minutes till tender. Drain and plunge into iced water to cool. Drain.
Melt butter in a saucepan. Add lime juice and Brussels sprouts and cooked till warmed through.
Transfer to a bowl. Top with popcorn, lemon zest and sea salt.