Preheat the oven to 140º C.

1.  Pound the mastic crystals to a fine powder and combine with the confectioners sugar and lemon rind. In the mixer beat the egg whites until they become firm.

2.  Add 2 tablespoons of confectioners sugar, continuing to beat for 1-2 minutes.

3.  Add the remaining confectioners sugar, sprinkling the powder over the bowl while working the mixer, until the meringue glistens and holds its shape. Empty the meringue into the cleanest possible pastry horn.

4.  Lightly butter a large, clean baking sheet and sprinkle it with a little flour.

5.  Use the pastry horn to squeeze out 24 egg-shaped meringues, sprinkle them with sugar and let them stand 10 minutes to absorb the sugar.

6.  Bake for 15 minutes, lower the oven to 120º C and bake for another 45-60 minutes. The meringues should be as white as milk with only the sugar crystals tinted gold in contrast to the surface as a whole.

7.  Remove the baking sheet from the oven and gently unstuck the meringues, turn them upside down and bake for 5-6 minutes to make sure their insides dry.