Make a custard by heating the cream, whisking it into the egg yolks, and then pouring the mixture back into the cleaned-out pan, then cook it, stirring, until it’s thickened. Pour it into a bowl and leave to cool a little, then stir in the condensed milk, tequila and Triple Sec (or Cointreau or Grand Marnier: I have used each of these in my time), lime juice and zest and then leave to cool completely before freezing in the normal way.

For utter, unapologetic perfection, serve the ice cream in margarita glasses that you’ve first dipped in lime juice and then into a half-and-half, salt and sugar mixture. But just scooped into bowls or cones, this is hard to beat.