Cupcakes: sift the flour, cocoa, baking soda, baking powder and salt into the bowl of a heavy mixer fitted with the paddle attachment; add sugar.
Turn the mixer on low and add, in order; water, milk, eggs, oil and vanilla; scrape down the sides of the bowl and beat on medium, briefly, to achieve a smooth batter.
Scoop the batter into muffin tins lines with paper baking cups; each cup should be about half full; slide the tins onto a baking sheet and bake at 325° until a toothpick inserted into the center comes out clean, about 30 minutes.
While cupcakes are cooling, prepare the frosting.
Frosting: Cream the butter in the bowl of a mixer, using the paddle attachment; beat in the corn syrup, vanilla and salt.
With the machine off, spoon in the cocoa; carefully turn the mixer on low so as to avoid death by cocoa inhalement; do likewise for the sugar, in three parts; last, add the cream then beat until fluffy.
When the cupcakes are completely cool, frost generously and shake on some sprinkles if you like.