Slice 4 hot cross buns in half and toast in a toaster, or under a preheated grill, until golden. Spread the halves with butter and leave to cool.
Meanwhile, cut the remaining 12 buns in half. Working with the top half of the buns, the half with the crosses on, roll out with a rolling pin until about ½ cm thick. Repeat until all the crossed halves are rolled out. Press the rolled out buns into a 12 hole muffin tray lined with clingfilm.
Chop the toasted hot cross buns into small pieces and add the to slightly softened ice cream, then mix to combine and place a scoop of the toasted bun ice cream into each muffin hole. Use Using a cookie cutter, stamp out circle from the ‘base’ buns halves that you have remaining and place on top of the ice cream then fold any overhang into the centre of the muffin tin.
Place the tray into the freezer for at least 4 hours.
To serve, remove the hot cross bun bombs from the muffin tray, peel of the cling film and leave at room temperature for 10 minutes before enjoying!