Place fruit in large saucepan with water.
Cover, bring to boil and simmer for 40 minutes or until pulpy.
Place pulp and liquid in a jelly bag, suspend over a large bowl and allow to drip freely overnight.
Measure strained liquid into a preserving pan and set aside ¾ cup sugar for each cup of liquid.
Bring liquid to boil; remove from heat and stir in the sugar until dissolved.
Return to a brisk boil and add pectin mix (if using – note that some varieties of guava contain less pectin), stirring to dissolve. Return to heat and boil briskly, skimming off any froth.
Pour in gin as jelly gets close to setting stage. To test setting, drip jelly from a wooden spoon.
When 2 drips connect, jelly is ready to set. Once at setting stage, remove from heat. Place a slice of blanched lemon into each sterilised jar and pour over guava jelly.
This Guava Jelly with a difference is equally delicious on toast or creamy Brie or blue cheese and served with Pinot Gris.