How to Make It
In a saucepan, bring the milk, water, sugar and cilantro to a boil; stir to dissolve the sugar. Transfer to a stainless steel bowl set in an ice water bath; stir occasionally until cool.
In a blender, puree the sorbet mixture. Strain through a fine sieve set over a bowl. Stir in the lime juice, tequila and salt.
Freeze the sorbet in an ice cream maker according to the manufacturer's instructions. Transfer to a shallow bowl, wrap with plastic and freeze until very firm, about 1 hour.
Variation To prepare a granita, pour the sorbet mixture made in Steps 1 and 2 into a chilled 9-by-13-inch baking dish. Freeze the mixture until ice crystals form around the edges. Using a fork, break up the crystals. Freeze the mixture until it begins to harden; break up the crystals again. Continue freezing and breaking up the crystals until the granita is completely frozen into a mass of soft, icy shards.
This sorbet is also delicious with clear rum instead of tequila.