Warning Bacon education ahead.
This

is a Bacon Sandwich - or Sarnie - note the use of bread
This

is a Bacon Butty - note the use of a Bap or Bun
Definition of Bacon Sarnie - What is the Meaning of Bacon Sarnie
And is the subject of research
BBC NEWS | UK | England | West Yorkshire | Scientists' 'perfect' bacon butty
The Formula
N = C + {fb(cm) . fb(tc)} + fb(Ts) + fc . ta
N = force in Newtons required to break the cooked bacon.
fb = function of the bacon type.
fc = function of the condiment/filling effect.
Ts = serving temperature.
tc = cooking time.
ta = time or duration of application of condiment/filling.
cm = cooking method.
C = Newtons required to break uncooked bacon.
And has "medicinal" uses
Bacon sandwich really does cure a hangover - Telegraph
Hungry now?