If you like plums, add more plum juice. Take the pitted plums and drop them in a food processor.
Grind them smooth. You can use water to grind them too.
Strain the juice.
Add the lemon juice. You can also add more later according to your taste. Add sugar to taste. Mine were pretty sweet thanks to the ripe plums hence I would have used probably about 1/4 to 1/2 cup.
Add enough water according to the consistency you require. Make sure that you add water keeping in mind the ice cubes that you might add which will melt and add more liquid to the lemonade.
Garnish with lemon slices and fresh mint.