1. Line a 9 x 5-inch loaf pan with plastic wrap. Combine 1/2 cup sugar, milk, honey, orange rind, vanilla extract, 1/8 teaspoon salt, cream cheese, and ricotta in a blender; process until smooth. Pour the mixture into a large bowl. Pour cream into a medium bowl, and beat with a mixer at high speed until stiff peaks form. Fold 1/4 cup whipped cream into ricotta mixture. Fold in the remaining cream.
2. Spoon mixture into prepared loaf pan. Cover with plastic wrap, and freeze at least 8 hours or until set. Remove semifreddo from freezer, and let stand at room temperature for 20 minutes. Discard top piece of plastic wrap. Invert loaf pan onto a serving platter, and tap to remove semifreddo. Discard the remaining plastic wrap, and slice semifreddo crosswise. Serve with orange sections and currants, if desired.