Combine currants, apricots, raisins, and bourbon in a small bowl. Let stand 1 hour or up to 4 hours.
Combine yeast and milk in a medium bowl; whisk until smooth. Stir in 1 cup flour until well blended; cover and let rise 30 minutes.
Combine 1/2 cup butter, sugar, and salt in a bowl; beat at medium speed with an electric mixer 3 to 5 minutes or until light and fluffy. Add orange rind and vanilla; beat 2 minutes. Add 3 cups flour alternately with eggs, beginning and ending with flour. Stir in yeast mixture. Turn out dough onto a floured surface, and knead until smooth while gradually folding in fruit mixture (8 to 10 minutes). Place dough in a buttered bowl, turning to butter the top. Cover with plastic wrap, and let rise in warm place (85°), free from drafts, 1 1/2 hours or until doubled in bulk.
Butter a 10" springform pan. Place dough in pan, pressing to evenly fill pan. Cover with plastic wrap, and let rise 1 hour, or until dough reaches top of pan. Bake at 350° for 45 minutes or until a wooden pick inserted in center comes out clean, shielding with foil after 30 minutes to prevent excessive browning. Remove from oven, and brush with 2 tablespoons melted butter. Cool in pan on a wire rack 5 minutes. Remove sides of pan, and allow bread to cool. Dust with powdered sugar, if desired. Serve with Mascarpone Cream.