To make the sponge, dissolve the yeast in 60 ml warm water in a bowl. Add 60 flour and stir to make a very loose dough. Cover the bowl with a plastic wrap and let rise in a warm place for at least 6 hours, or overnight.
In the bowl of your mixer, combine the butter, eggs, yolks, sugar, milk, and vanilla seeds. Add in the starter dough. Gradually add the flour, beat on low speed just until dough begins to leave the sides of the bowl and pull together. Increase speed to medium, and beat until the dough becomes smooth and elastic, about 5 minutes.
- Place the dough in a greased bowl and turn it once to coat both sides. Cover bowl of dough with plastic wrap, and let rise for 5 hours in a warm place until doubled in size. With your hands, flatten the dough on a lightly floured surface into a rectangle. Evenly distribute the lemon zest, raisins, apricots, and almond over the dough. Fold the dough to seal the fruit and knead to distribute the fruit throughout the dough.
- Line a 8-inch mousse ring with parchment paper that has been well buttered on both sides and set it on a baking tray. Place the dough in the mold, cover with a towel, and let rise for 45 minutes in a warm place. Preheat the oven to 200C/400F.
- Make a cross on the top of the bread with a sharp knife and insert a cube of butter. Bake the bread on the middle rack of the oven for 10 minutes. Reduce the heat to 180C/350F. Continue to bake for 30-35 minutes until the surface is golden and crispy. Place the bread on a rack to cool for 30 minutes before removing it from the mold. Dust the bread with icing sugar if desired. Be sure the bread has cooled completely before wrapping for storage.