Spread the crushed graham crackers on a plate. Pour some simple syrup onto another plate. Dip the rims of your glasses into the syrup, then into the crackers to coat them.
In a cocktail shaker, muddle the mint leaves with the lime juice. Fill the shaker with ice and add the rum, cream, and additional simple syrup. Shake vigorously until the outside of the shaker gets frosty, about 20 seconds.
Fill your glasses with ice and strain the mojito mixture into them. Garnish with extra mint leaves and a slice of Key lime.
Sip on this delightful concoction and let the flavors whisk you away to a tropical paradise!