Microwave Cheese & Onion Sandwich

Microwave Cheese Onion Sandwich Toastie Recipe

An easy microwave cheese & onion sandwich recipe that is a great snack at home, or can even easily be bagged up and taken to work if you’ve a toaster and microwave available! This is quick mug cooking, using a mug to create this popular hot sandwich filling!  The best way to whip up a snack in a commercial break if you’re watching the telly in the evening!


  • 2 pieces of bread
  • 1 small onion, or ½ a medium onion, sliced
  • 30-50 grams of cheese
  • Tiny splash of oil
  • Entirely optional: tiny bit of mustard (powder or ready made), tiny splash of Worcestershire sauce (for that Welsh Rarebit twist)


  1. Just pop the sliced onion into a microwave safe mug with a TINY splash of oil, then stir so the onion is coated in the oil.  Optionally microwave the onion for 1 minute on full power.
  2. Add the cheese to the mug – the smaller you cut it the faster it will cook, so you can grate it or roughly cut it into lumps.  Add any additional/optional flavourings you like, such as mustard or a tiny splash of Worcestershire sauce (I usually don’t bother)
  3. Microwave the cheese and onion sandwich filling in the mug, stirring the mix every 30 seconds until the cheese is melted.
  4. Toast your bread.
    Microwave Cheese Onion Toastie Sandwich
  5. Pour the hot cheese and onion mix over one slice of the bread, pop the second slice on top. Cut, serve, eat!

TIP: When you make this mix it can be a little runny and you might wonder if it’ll all fit onto the toast.  If you let the hot cheese and onion cool down for 1 minute it’ll become less runny.  I’m generally too impatient to wait!