To make the white chocolate snow, melt the butter and white chocolate in a heatproof bowl set over a pan of simmering water, stirring occasionally. Remove from the heat and fold in the cream and then allow to cool. This can be used chilled or at room temperature whichever you prefer.
Preheat the oven 350°F. Grease six mini pudding molds and dust with cocoa powder. Melt the butter in a saucepan. Remove from the heat and gently stir through the chopped chocolate until melted.
In a medium-sized mixing bowl, whisk together the eggs and sugar until they become pale and thick. Pour in the chocolate mixture, then sift in the flour. Using a spatula, fold the mixture together until it is evenly combined.
Place the greased pudding molds on a baking sheet and divide the chocolate batter among them. Place in the oven on the middle shelf to cook for 12 minutes. When cooked, remove from the oven and leave to rest for at least 1 minute. Then run a mini spatula around the inside edges to loosen the puddings, invert onto plates and spoon a heaped tablespoon of white chocolate snow over each one, then decorate with the holly and berries, if desired.