Preheat the oven to 170C/325F. Line two baking trays with a silicone mat or baking parchment.
Using a hand whisk or mixer, whisk the egg whites to stiff peaks. Fold in the ground almonds, cocoa powder, caster sugar, dried cranberries and vanilla extract. Slowly stir in the amaretto. Add just enough so that the mixture is a thick paste that can be formed into a ball in your hand (it should be sticky, but should hold its shape).
Place the caster sugar and icing sugar for rolling on two separate plates. Using a teaspoon, scoop out a chunk of the cookie mixture and roll it into a ball in your hands (about the size of a walnut). Roll it in the caster sugar, then roll it in the icing sugar and place on the baking tray.
Repeat with the remaining dough until you've used it all up. Leave a bit of space between the cookie balls as they will expand slightly during cooking.
Use your finger to squash the cookie balls a little, then place in the oven to cook for 15 minutes.
Take out of the oven, and leave to cool on the baking tray before serving.
*This recipe works best with store-bought ground almonds. Home-ground almonds can give the cookies variable results. I believe this is due to the amount of oil produced during the grinding process, depending on how long you grind them for.Once cooked and cooled, stored these cookies in an air-tight container at room temperature, where they should keep nicely for up to two weeks..Nutritional Information is per cookie.