Combine the powdered sugar, cinnamon powder, water, lemon juice, ground almonds, ground hazelnuts, and grated orange peel in a bowl. Knead together for about 5-10 minutes until you have a uniform dough. Roll out the dough on a surface lined with aluminum foil. Cut out star shapes using a mold. Let the stars dry at room temperature for 4 hours.
Preheat oven to 250°C (482°F). Line a baking sheet with baking paper and arrange the cinnamon stars on it. Bake for 3 to 5 minutes, watching carefully to prevent overbaking. Cool completely.
Sift the powdered sugar and combine it with cinnamon powder. Add water drop by drop while stirring until you have a chewy frosting. Coat each cooled cinnamon star with the frosting. Allow the frosting to dry completely. Store in a tin lined with aluminum foil.