Flatten the capsicums, skin side up, onto a tray lined with foil.
Grill until 90% of the skin is completely black (the edges will stay red, which is fine).
Remove and wrap the foil around the capsicum pieces to let them sweat until cooled (about 30-40 mins). Unwrap and peel off skins and save the capsicum flesh pieces. Put pieces in a glass container, seal and keep in the fridge for up to 5 days. I also save the capsicum juices that comes out in the same container.