Place your martini glasses in the freezer to chill. If you can't do this step, then place lots of ice and water in each glass and allow it to chill. Empty the glasses before filling them with the cocktail's ingredients.
Prepare the simple sugar syrup.
Follow video instructions on how to remove the sweet, white fruit from the red, fuzzy exterior of the fresh rambutan.
Follow the second video instructions on how to remove the seeds from the white fruit.
With an immersion blender, mash up the white rambutan fruit; do this for a good 3 - 5 minutes.
Place tall of the crushed rambutan fruit and its liquid into a cocktail shaker.
Add the vodka,
Add the limoncello.
Add the simple sugar syrup.
Add a squeeze of fresh lemon juice.
Fill 2/3rds with ice cubes.
Shake the mixture in the cocktail shaker for about 30 seconds.
Strain the rambutan/limoncello/vodka mixture into the chilled martini glasses.
Garnish lemon slices and/or mint leaves.
Serve immediately while chilled.
Salute'!