I'd forgotten about the way they are made. When we were in Madrid, way back in time, when it was too hot to be outside, we went into a cafe and they made these. They are almost all slushy ice but with the tequila and orange liquor added, not to mention the salt around the rim. This was in Dunedin and at a local Joe's Garage restaurant. You can't drink it fast - too cold but it is divine!
Had family for lunch yesterday and made a margarita mousse for dessert! Ever so delicious ;-)