Preheat the oven to 350°F.
For the cupcakes:
- Combine 1 1/4 cups of the sugar, the flour, baking powder and salt in a large bowl.
- Combine the egg yolks and water in a small bowl. Add to the dry ingredients in 3 stages, stirring until smooth. Add the melted butter and vanilla and stir until well incorporated.
- In a large bowl, whisk the egg whites and the remaining 1/2 cup of sugar to soft peaks. Gently fold the whites into the cupcake batter, just until incorporated.
- Divide the batter into a 12-cup baking tin and bake until a toothpick inserted into a cupcake comes out dry, about 20 minutes.
For the truffles:
- In a small saucepan add the cream and bring just to a boil over low heat. Put the chocolate into to a medium bowl and pour in the hot cream. Let stand for 1 minute, then stir until smooth. Stir in the butter and mix until incorporated.
- Put plastic wrap directly on the surface of the chocolate and refrigerate for 1 hour.
- When the chocolate is cool, transfer to a pastry bag fitted with a large tip.
For the batter:
- In a deep-fryer or heavy-bottomed pot, heat enough peanut oil to come halfway up the sides of the pot, to 350°F.
- Combine all the batter ingredients in a large bowl and stir until just combined. Do not overmix. Cover and refrigerate until ready to use.\
- With a paring knife, remove the middle of the cupcakes, but leave the tops intact. Using the pastry bag, fill the holes with the chocolate. Replace the top firmly.
- Coat the cupcakes in batter and deep-fry, in batches, until golden brown on all sides. Remove from the fryer and drain on paper towels for a few seconds. Transfer to a serving platter, then indulge.