Read through the entire recipe first. Many notes are include for ease and convenience.
Lightly grease a large mixing bowl with olive oil, set aside for later. Prepare a baking sheet with parchment paper or a silicone baking sheet and set aside.
In the bowl of a stand mixer (or a separate large mixing bowl), combine the warm milk, sugar and yeast, and gently mix by hand to combine. Leave the bowl undisturbed for 5-10 minutes for the yeast to activate. If the yeast doesn't bloom and create a thick frothy layer after 5-10 minutes, it means the yeast is not active and the dough will not rise, discard and try again with a fresh batch of yeast.
Slowly add the lightly beaten eggs and vanilla to the yeast mixture, whisking as you add, until just combined. Adding in slowly and gently mixing will help temper the eggs if the milk is still quite warm.
Add only 2 cups (250 g) of the flour (reserving the rest for the second rise) along with the ground cloves, cinnamon, and nutmeg to the yeast mixture. Using a mixing spoon or a silicone spatula, combine just enough to incorporate all of the ingredients, scraping down the sides of the bowl. Note that the mixture will still be quite sticky and very wet, do your best to gently mix and scrape from the sides and bottom, removing as much sticky dough from your whisk or spoon. Cover the bowl with a tea towel and let it rest for 30 minutes in a warm, draft-free area.
After 30 minutes, the wet dough will have puffed-up and inflated a bit.
From the reserved flour, separate out 1 cup and add the salt, briefly mix to combine. Leave the remaining 1/2 cup or so of flour set aside, you will use it in a bit if the dough mixture is still too sticky to handle. If using a stand mixer bowl, secure the bowl to the mixer, and begin by using the paddle attachment. Add the salted flour to the bowl, ½ cup at a time, mixing well after each addition. Scraping down the sides as needed. Add the softened butter into the bowl, and briefly mix again.
Add the raisins and cranberries and mix to combine.
Once the dough has formed into a cohesive mass, switch to the dough hook attachment and begin to knead. If the dough is still too wet to work with, begin to incorporate some of the reserved ½ cup of flour, only a little at a time, until the dough starts to firm up and isn't sticking to the sides of the bowl. It is common to not use all of the reserved flour, so don't feel compelled to toss it all in. Much will depend on the age of the flour, the humidity and temperature of your environment and altitude, so start with less - you can always add more. The end result should be a dough that is soft and pliable and still a little sticky, but not so much that it is unmanageable. Adding too much flour will create a dry hot cross bun. Any leftover flour can be applied to the measurement for the making the cross.
Transfer the dough to a lightly floured work surface and knead just briefly to make sure the cranberries and raisins are distributed as evenly as possible. Form the dough into a ball. Place the dough into the lightly oiled bowl. Cover and let it rest for 30 minutes in a warm draft-free area.
After 30 minutes, the dough should have increased in size. Divide the dough into 12 equal pieces. Roll each piece into a ball shape.
Place the 12 balls of dough onto the prepared baking sheet in 3 rows of 4, setting them close together, but not so close they touch (when they bake and rise, they will fuse together to create a pull-apart style). Cover and let it rise for one hour.
Prepare the mixture for the cross. Mix 1/2 cup flour (weigh 63 grams for accuracy) and 6 tablespoons water together to form a thick paste. The consistency should be easy to pipe, but thick enough that it will not run, make sure there are no lumps. Thin with a little more of the reserved water only if necessary. Spoon the paste into a piping bag or a large plastic storage bag.
Preheat the oven to 400 F. (204 C). Once the buns are ready for baking, use the piping bag or the plastic storage bag with the corner snipped off, and gently squeeze the paste mixture across the buns, in both directions to form a cross. Note: It's easiest to go one way across all the buns and then in the other direction across all the buns. Bake 15-20 minutes or until golden brown.
In the meantime, prepare the glaze by making a simple syrup. Bring the sugar and water to a low boil in a small saucepan, stirring until all the sugar has dissolved. You'll know it's ready when you don't feel any grainy bits of sugar at the bottom of the pan. Brush the glaze on the buns when they come out of the oven and are still piping hot. Allow them to cool to the touch, about 5-10 minutes, before serving.
Best served warm with butter. Store the hot cross buns in an airtight container, at room temperature. Best if consumed within a day.
Notes
* When in doubt, weigh the flour for accuracy. 125 grams is a proper cup of flour. 62.5 - 63 grams, is an accurate 1/2 cup. Dipping a measuring cup into a bin of flour will pack the flour and will result in adding more flour to the recipe than is required - too much flour will produce a dry hot cross bun.