Bring the cream and the butter to the boil. Remove from the heat and stir in 250 g chocolate. Chop the leaves from the Atsina Cress and mix into the chocolate mixture. Pour the chocolate mixture into a deep container and allow to stiffen in the fridge. Scoop balls from the ganache using a warm parisienne scoop and put in the freezer.
Melt the rest of the chocolate and roll the balls through it. Place on a grid and place in the fridge.
Serve on a plate and garnish with Atsina Cress.