We first had this at Rodizio Grill. It is Allan's favorite drink. It is a little labor intensive (harder than Koolaid). But it is well worth the effort!
1/2 cup sugar
3 tablespoons sweetened condensed milk
3 cups water
½ can 7-up (optional)
Wash limes thoroughly. Cut off the ends and slice into eight wedges. Place limes in a blender with water.
*Blend in blender, pulsing 5 times. Strain through a fine mesh strainer to remove rinds. Squeeze as much juice and water as you can. Return juice and water to blender.* Add milk, sugar and ice. Blend until smooth.
Stir in 7-up.
*I whiz the limes in the blender for a minute before I add the water. Then I whiz it again. Then I pour the limey water through a strainer (with sort of large holes, I use a Tupperware one) into a pitcher. Then I rinse the blender and I pour the limey water through a fine sieve back into the blender. Then rinse out the pitcher.