Heat the rum and raisins slightly. Macerate for a few hours.
Place the pastry scraps and water in a mixer bowl and mix with a paddle to a smooth consistency. You may have to adjust the amount of water, depending on how many dry items you are using. Mix until you have a very firm, smooth dough, approximately 10 minutes. Add the crushed nuts and the chocolate and mix until combined. Incorporate the rum and raisins.
Place on a sheet pan lined with baking paper. Refrigerate until the filling is firm before shaping. If the mixture is too soft to work with, add more scraps from dry items, finely ground, to absorb moisture. If the filling is dry and crumbly, mix in enough buttercream or ganache to bring it to a workable consistency.