Place condensed milk, potatoes, vanilla, cardamom, coconut sugar in a saucepan and bring to a boil, reduce to a low flame and let cook uncovered for about 20 minutes, stirring frequently.
Remove from heat and let mixture cool.
Add in the cashew and egg, mixing well to combine.
Preheat oven to 350°F.
Bake in a parchment lined baking tray for 15 minutes.