To cure the common cold -

  1. Take two slices of bread, a wedge of salted butter, one small onion, one jar of English Mustard, one jar of Marmite, three eating knives and chopping knife.
  2. Butter the bread.
  3. Thickly spread the mustard on one slice, the Marmite on the other other using a separate knife for each. Otherwise you get buttery mustardy marmite and every combination thereof which is a bit gross, especially as it looks like an infected gut-wound.
  4. Dice your onion. Evenly place the diced onion on the Marmited sliced of bread.
  5. Place the mustarded slice of bread to form the top of sandwich.
  6. Press down firmly on the top - you should do this without forcing the filling out of the sides. Just enough to get it all firmly stuck together.
  7. Bite. Chew. Swallow. Breathe clearly. You're cured!

In all fairness, any bug that can survive this treatment deserves its chance to kill you.