Pour full-fat milk into a heavy-bottomed pan and bring it to a gentle boil.
Simmer on low heat, stirring regularly, until the milk reduces slightly.
Add condensed milk, cocoa powder, and sugar, then whisk until smooth.
Add chopped dark chocolate and stir until completely melted.
Add cardamom powder and mix well. Allow the mixture to cool completely.
Pour into kulfi molds and freeze for at least 6 hours or overnight.
Remove from the molds, garnish with chocolate shavings or chopped nuts, and serve chilled.