Pulse the walnuts, dates, and salt in a food processor until sticky. If the mixture is too dry, add a teaspoon of water at a time until it becomes sticky like dough. Divide into four parts, spoon into muffin tin, and refrigerate until set.
Combine the avocado, maca, lucuma, honey and vanilla bean in a food processor. Blend until smooth. Fill the tart shells with the mousse and decorate with sliced figs.