To make the dough, put the warm milk and water in a large bowl, and sprinkle a pinch of the sugar and all of the yeast overtop; let sit for 5 minutes, until it gets foamy. Add the flour, remaining sugar, potato flakes, egg, butter and salt and blend until you have a sticky dough; add the raisins and candied citron and knead (in your stand mixer with a dough hook or on a lightly floured countertop) until smooth and elastic. It should be slightly tacky. Place in a greased bowl, cover with a tea towel and let sit for an hour, until doubled in bulk.
Punch down the dough and divide it into 12 pieces - I find this easiest to do by cutting it in half, then each half in half, then each piece in three. Then take each piece and cut it into about 6 pieces - this is easy to do with a dough scraper/bench knife, and they don't all have to be equal.
Line 12 muffin tins with paper liners and spray the papers with nonstick spray. Mix the sugar and cinnamon together in a small bowl and roll each piece of dough in it to coat, then place in the tins - so you'll have about 6 pieces in each tin. Sprinkle the remaining cinnamon sugar overtop. Cover loosely with a tea towel and let sit for another hour. Toward the end of the rising time, preheat the oven to 350°F.
Bake for about 20 minutes, until golden. In a small dish, stir together the sugar and water and brush/dab over the tops of the buns while they're still warm. Stir together the icing sugar and milk or cream and drizzle over the cooled buns.
Serving Size Makes 12 pull-apart hot cross buns.