Easter Fruit Buns

1 Make the sponge: Pour the milk into a large bowl. Add the yeast, and let dissolve. Whisk in a cup unbleached all-purpose flour, then cover the bowl and leave in a warm place until it has doubled in size and is very frothy. This should take about 30 minutes, though it has taken upwards of an hour for me depending on the weather.
2 Prepare ingredients for the buns: Measure the currants, raisins, cranberries and apricots into a bowl. Cover the dried fruit with hot water, and let stand for 10 minutes. Drain the fruit, then return to its original bowl, and stir in the rum before setting aside.
3 In another bowl, measure out and beat the 2 whole eggs and 2 of the yolks.
4 Once the sponge is ready, pour the beaten eggs, melted butter and vanilla extract into the sponge mixture, and stir together. Fold in the rum-soaked fruit, then set the sponge and fruit mixture aside.
5 In the large bowl of your stand mixer, measure out 4 cups of unbleached all-purpose flour, the sugar, salt, anise seeds, cardamom, cinnamon and the orange and lemon zests. Whisk together.
6 Pour the sponge mixture over the flour mixture and combine using the dough hook of the stand mixer, starting the mixer on a low speed and turning it up once the loose flour has started being incorporated into the dough.
7 When the dough comes together, allow the stand mixer to knead the dough for a few minutes before turning off the appliance and transferring the dough to a greased large bowl.
8 Cover the bowl containing the dough with plastic wrap or a damp towel, and let rise in warm place until it has doubled in size. This should take around 45 minutes.
9 Once doubled in size, punch the dough down and knead it lightly before breaking it down into 16 buns. (I knead the dough into one loaf, then split into two round loafs. From there, I slice is like pizza. Each round loaf breaks down neatly into 8.)
10 Place the buns side-by-side on a nonstick baking mat. Be sure to leave at least 1/2"-1" between the buns, as they will rise again.
11 Cover the loaves with plastic wrap or with a damp kitchen towel, and let rise until doubled. This should take around 30 minutes.
12 When the loaves have doubled in size, preheat the oven to 350°F.
13 While the oven is preheating, make the egg wash. Using the remaining egg yolk and the heavy whipping cream, beat the ingredients together with a fork.
14 Brush the buns generously with the egg wash, then sprinkle each bun with a little turbinado sugar.
15 Transfer the buns to the oven. Bake on the middle rack for 35 minutes or until the buns are a dark, glossy brown.
16 Once cooked through, transfer the loaves to a cooling rack and allow them to cool down completely before enjoying.