However--according to her--the fresh picked peppermint from the garden was critical, and maybe that had something to do with it.
In any case, I believe this recipe is what she used.
3 sprigs fresh peppermintPut sugar in the bottom of the glass (collins glass or a silver julep cup). Add water. Bruise 2 peppermint sprigs and place inside the glass. Fill the glass with crushed ice. Pour in the bourbon. Garnish the julep with the remaining peppermint sprig.
1 teaspoon fine white sugar
1 teaspoon water
2 ounces bourbon
crushed ice