In the saucepan whisk together sugar and cornstarch. Add cherries, liqueur, vanilla, and cinnamon and bring to a boil over moderate heat, stirring occasionally. Simmer and stir for about 2 minutes and transfer to the casserole dish.
In the mixing bowl, whisk together the flour, baking powder, baking soda, and sugar. Pour the melted butter into the measuring glass with the cold buttermilk and stir until the butter forms small pieces and floats in the milk. Make a well in the dry ingredients and pour the buttermilk mixture into the well, folding the dry ingredients into the liquid just until the dry ingredients are wet. The mixture will start to poof and rise, so work quickly.
Use the scoop to form the biscuits and drop them over the cherries, spacing apart. Brush dough with melted butter and sprinkle some cinnamon sugar mixture over the dough. (optional) You may have some dough left over, and you can just drop those biscuits onto a baking sheet and bake for about 25 minutes.
Bake in the preheated oven until the cherries are bubbling and the biscuits are golden brown, about 35 to 40 minutes. Cool until the cobbler is just warm, not too hot. Serve with vanilla ice cream.