Mix the water in the recipe with 150g of the recipe's flour and the yeast in a bowl. Let it rest for 30 minutes. When you look at it after that time it should look very fluffy, this is called a "sponge". If you don't see any activity it's because your yeast isn't working.
As the yeast is activating, hydrate your raisins in boiling water for 10 minutes so they're not too dry. Place them on a colander and let them release the excess water.
Add the rest of the flour (450g) to the sponge along with the sugar, salt, eggs, egg yolk, rum, orange and lemon zest and vanilla. Mix by using your hands or the hook attachment on an electric mixer. Knead for 20 minutes by hand or 10 minutes on medium heat with the electric mixer. The dough should be slightly sticky, you can adjust the texture by adding 1 tbsp of flour or water at a time. This will depend on the size of your eggs.
After kneading, add the butter at room temperature, one tablespoon at a time as it incorporates to the dough. At first, it will be harder to incorporate and will get easier as you go. By hand is a bit messy but totally doable! Check out my brioche recipe where I do this by hand on video.
Once the butter is completely incorporated, knead a bit more until the dough looks smooth and shuiny. Add the raisins / chocolate / nuts or whatever you want to add and mix them in.
Place the dough on a bowl, cover it with plastic and place in the fridge for at least 8 hours and 24h tops.
Knock down the dough and flatten it slightly. Fold it again at the centre like a parcel. Turn it so that the place where the dough joins together is against the countertop. Spin it with two hands to seal it and also try to make it thinner and taller so it fits into the paper mould. Place the dough into the paper mould, made for 1kg.
Let the dough proof for 3 hours in a warm spot.
Preheat your oven at 180°C/350°F. Before baking, score the top of the dough in a cross using a lame or an old-style razor blade.
Bake the Panettone for 30 minutes with top and bottom heat if your oven is electric, and then 40 extra minutes with only bottom heat. If you have a gas oven, then the heat comes only from the bottom, so cook it directly for 1h10min. If it's golden enough after 30 minutes, place tin foil on top.
When you remove it from the oven, it needs to cool down hanging upside down, this prevents the crumb from becoming thick. For that, you want to use a skewer and poke it through the panettone close to the base. The paper will help it stay in place and not break the crumb. Use the skewers to hang the panettone upside-down between two objects.
Cut a piece and enjoy :). My favourite way to enjoy it is toasted with butter.