To make the cranberry mayo, mix all of the ingredients together and set aside.
Grill the bacon rashes until crispy and drain onto kitchen paper. Toast the bread on both sides and butter, to assemble each sandwich, layer one piece of toast; a lettuce leaf, sliced turkey and some cranberry mayo. Place a second piece of toast on top and layer again, with more mayo, streaky bacon, lettuce and the tomato.
Season well with sea salt and black pepper and top with another piece of toast, cut in half and spike each half with a cocktail stick and serve with potato crisps.