First, pre-heat the oven on 200 degrees. Then, add marzipan, ground almonds, lemon juice, egg yolk and cinnamon to a bowl. Add sugar and mix until well combined.
Next make a role out of the mass, 2 cm thick and divide into 20 pieces. Form little horns out of the 20 pieces and place them on a baking tray lined with parchment paper.
Mix the eggwhite with the water and break down the almond flakes a little bit and add them to a small bowl. Dip the almond horns in the eggwhite mixture and then in the almonds and place back on the baking tray.
Bake almond horns for 10 minutes, take them out and place on a cooling rack.
Once cooled completely, melt the chocolate on medium heat. Once melted, dip the chocolate horns into the chocolate and place back on the baking tray. Let them cool completely.