Mix together the sugar and cinnamon, set aside. Peel, core, and slice apples. To make clean-up easier, line a sheet pan with aluminum foil to catch the "drips". Place empty ramekins on the pan for filling. Pack each ramekin 1/2 full with a mixture of the sweet and tart apple slices. Sprinkle cinnamon sugar mixture over the top. Pack remaining portion of the ramekin with mixture of apples. The apples should mound slightly over the top of the ramekin. Sprinkle cinnamon sugar mixture over the top.
Mix together sugar and flour. Using a pastry blender, cut in the cold butter till mixture resembles course crumbs. Sprinkle topping liberally over the top of the apples. (Store extra topping in the refrigerator for the next time!)
Bake at 400 for 40-45 minutes until top is golden brown. Cool slightly.
Serve slightly warm with a dollop of whipped cream or creme fraiche; or if you want to be really decadent, vanilla bean ice cream!