Panettone has a reputation for being extremely difficult to make, and the reason is because this bread has a very long preparation time. The dough doesn't rise only once – it rises three times and each rise takes a few hours! The dough has to rise in a warm place. An easy to do this is to place the bowl of dough into the oven and turn on the oven light. This will keep the oven temperature above 80 degrees Fahrenheit.
1) In a small bowl, combine the water and milk, sprinkle over the yeast and let sit for 5 minutes. add 4 tbsp of flour and 1 tbsp of sugar to the yeast mixture, mix to combine and cover with plastic wrap. let sit in a warm place and let it rise until doubled in volume, about 30 minutes.
2) In the bowl of a standing mixer, whisk together the eggs, sugar, vanilla, lemon zest and orange zest, add the yeast mixture and wish until all combined. Using the dough hook attachment, turn the mixer on low and add the flour and salt, turn to medium and let it mix for about 5 minutes. Add the butter and mix until it's incorporated.
3) Oil a large bowl with vegetable oil and set aside. after 5 minutes, add the raisins and citron and mix for a few more seconds. dump mixture onto a well-floured surface and work it for just a minute or until it comes together, place it in the oiled bowl and brush some more vegetable oil over the top to stop a crust from forming. cover tightly with plastic wrap and put it somewhere warm for 3 to 4 hours or until tripled in volume.
4) Spray a panettone mold or an 8'" cake pan with nonstick spray and set aside. once the dough has risen, dump it on a floured surface and pull it together, place it in the panettone mold and brush the top with some melted butter. cover again with plastic wrap and let it rise again for 2 to 3 hours or until tripled in size once again.
5) Preheat the oven to 350 degrees. brush the top of the panettone with some egg wash and bake into your preheated oven for about 45 minutes or until when a skewer or dried piece of spaghetti inserted in the center comes out clean.
6) Let it cool for about 20 minutes and serve!