To a mixer with the dough hook attached, add the flour, salt, sugar and yeast. Turn it on for a few spins to mix and then turn off. Add the softened butter, eggs, milk and 1/4 cup of water. Mix and add more of the remaining water, a little at a time, until all the flour has been incorporated into the dough from sides of bowl. You don't need to use all of the remaining water if you don't have to. DOUGH SHOULD BE SOFT, NOT SOGGY.
Knead for 5 minutes on hook, OR if kneading by hand, turn dough on to a lightly floured surface and knead by holding the dough with one hand and stretching it with the heal of the other hand, then folding it back on itself. Repeat for 5 mins until smooth and elastic.
Put the dough in a lightly oiled bowl. Cover with oiled cling film or light towel and let rise in a warm place for 1 hr or until doubled in size and a finger pressed into it leaves a dent (See Note 2).
With the dough still in the bowl, add the golden raisins, currants, citrus zest, diced apple and cinnamon. Knead into the dough, making sure everything is well distributed. Leave to rise for 1 hr more, or until doubled in size, again covered by some well-oiled cling film to stop the dough getting a crust.
Divide the dough into 12 even pieces. Roll each piece into a smooth ball on a lightly floured work surface by cupping the dough piece with your hand and moving in a circular motion, working the dough into a ball.
Arrange the buns on one or two baking trays lined with a silpat silicone mat or parchment paper, leaving a little space for the dough to expand. Cover (but don’t wrap) with more oiled cling film, and set aside to proof for 1 more hour.
Preheat the oven to 425°F.
Mix the flour with the water to make the paste for the cross – it should be a thick paste. Spoon into a piping bag with a small nozzle, or plastic bag with an end tip cut off. Pipe a straight line along each row of buns, then repeat in the other direction to create crosses. Bake for 20 mins on the middle shelf of the oven, until golden brown.
Heat the apricot jam plus 1 teaspoon of water in a microwave for 30 seconds to melt, then sieve to get rid of any chunks if needed. Brush over the top of the warm buns and allow to cool slightly. Serve with more jam and butter if desired.