In a small saucepan combine chopped dates, dried chopped cherries, sugar, salt, water and brandy, if using. Bring to a boil, reduce heat and simmer uncovered for 10 minutes or until dates and cherries are very soft and mixture has thickened. Set aside to cool. Transfer mixture to a small bowl when cool and refrigerate overnight. Take mixture out of refrigerator and allow to come to room temperature before using as filling in sourdough cinnamon rolls.
Measure out stirred down sourdough starter into a large bowl. Add milk, vanilla extract, melted butter, salt and 2 cups flour. Stir/knead this together to make a very sticky dough. Add up to 1 cup more flour if needed. Turn out onto a floured surface and knead by hand. Sprinkle in the baking soda and make sure it is thoroughly incorporated. Roll dough into a ball and place it in the bottom of a greased bowl. Cover the bowl with plastic wrap and place in a warm area to rise. This rise should take 2 to 3 hours. The dough should double in size. When the dough has risen, turn it out onto a floured surface. Pressing all the air bubbles out as you go. Roll the dough into a rectangle, roughly 9 x 18.
Mix together sugar and ground cinnamon. Brush the rolled dough with 2 tablespoons melted butter. Sprinkle with 1/2 of the cinnamon/sugar mixture. Spread cherry/date filling over cinnamon/sugar mixture. Sprinkle with rest of cinnamon/sugar mixture. Starting on one of the long sides, roll the dough into a long log. Slice log into 12 rounds and place rounds, cut side down in buttered glass 2 quart baking dish. Cover with plastic wrap and let rise for 2 hours or until doubled in size. Bake rolls at 350 for 20 minutes and top is golden brown.
Make Vanilla Icing: Whisk together all icing ingredients. Remove rolls from oven. Drizzle icing over rolls in pan while rolls are still hot. Serve warm.