Place the ricotta in a fine mesh sieve or in a colander lined with cheesecloth, cover with plastic wrap, refrigerate, and allow to drain overnight. It should be very well drained. While the ricotta is draining, combine the candied orange rind and brandy and let sit, covered, until the orange has absorbed some of the brandy.
Once the ricotta is well-drained, transfer to a bowl, add 1/2 cup of the superfine sugar and mix well. Add the egg yolks, 1 at a time, and mixing well after each addition. Add the salt, potato starch, grated orange zest, cinnamon and nutmeg. Stir to combine well then cover with plastic wrap and refrigerate for at least 1 hour before using.
Preheat the oven to 375 degrees F. Lightly butter 8 1/2-cup ramekins and coat each ramekin with some of the granulated sugar.
Beat the egg whites until foamy. While continuing to beat, add the remaining 1/4 cup sugar little by little and continue beating until the whites form soft peaks. Drain the orange rind and discard any unabsorbed brandy. Add the drained orange rind and the egg whites to the ricotta mixture and fold in gently but thoroughly. Divide the mixture evenly among the ramekins and place the ramekins in a baking dish. Add enough hot water to come almost to the level of the ricotta filling and bake, uncovered, until the timballi are puffed and golden, about 25 minutes. Place the cocoa powder in a small sieve and sprinkle cocoa powder over the tops of the timballi. Serve immediately. (Alternatively, timballi may be served either warm or at room temperature.)