2 Zest 2 of the limes and reserve. Now, take all 4 limes and remove the peels and pith (the white coating between the lime flesh and peel).
5 Add the peeled limes to a blender with the cold water. Blend for 20 to 30 seconds. Place a fine-mesh strainer over a bowl and pour the blended liquid through the strainer. You should be left with a little bit of pulp which you can use for other recipes or compost.
3 Pour the strained liquid back into the blender with ice, the reserved lime zest and the sweetened condensed milk. Blend until frothy.
4 Enjoy with extra ice and if you're in the mood, you can absolutely add a splash of your favorite alcohol too.
