Make the apple pie filling
In a large saucepan over medium heat, combine diced apples, brown sugar, lemon juice, vanilla, cinnamon, nutmeg, ginger, salt, and butter. Cook, with a lid on, stirring occasionally, until the apples soften, about 8-10 minutes. In a small bowl, whisk together cornstarch with 2 tablespoons of water until smooth. Pour this into the apple mixture and stir constantly for 1-2 minutes until thickened. Remove from heat and let cool until warm but still pourable. Keep it warm while you work.
Prepare your pan
Grease a 9x13 inch baking pan generously with butter or cooking spray.
Prepare cinnamon sugar coating
In a shallow bowl or plate, whisk together granulated sugar, cornstarch, and cinnamon. Set aside for dipping.
Ball, Dip and Coat
Dump dough out onto a greased surface. Pinch a golf ball size chunk of dough off. Working with one ball at a time, dip it into the warm apple pie filling, coating generously on all sides grabbing apple chunks with. Immediately roll in the cinnamon sugar mixture to coat completely. Place in the prepared pan. Continue until all balls are coated and arranged in the pan, touching each other.
Second rise
Cover loosely with plastic wrap or a damp towel and let rise for 1-2 hours at room temperature, or until puffy and the balls have grown together. They should jiggle slightly when you shake the pan.
Add remaining filling
After the second rise, pour or spoon any remaining apple pie filling over the top of the proofed focaccia.
Bake
Preheat oven to 425°F (220°C). Bake for 35-40 minutes, or until deep golden brown on top. If the top is browning too quickly (check around 25 minutes), tent with foil. The internal temperature should reach about 200-205°F. Cool in the pan for 10 minutes.
Make the Caramel Glaze
Make caramel
In a microwave-safe bowl, combine granulated sugar and water. DO NOT STIR. Microwave on high for 1 minute, then check. Continue microwaving in 30-second intervals, watching closely (total time will be 2.5-3 minutes). The mixture will turn from clear to golden to amber. You want a medium amber color. CAUTION: The sugar mixture is EXTREMELY hot!
Add cream and butter
Carefully stir in warmed heavy cream (it will bubble up dramatically!), butter, vanilla, and salt. The mixture will seize up at first but keep stirring. Let cool for 5-10 minutes until just warm to the touch.
Finish glaze
Whisk in powdered sugar until smooth. The glaze should be pourable but have some body to it.
Glaze
Drizzle the caramel glaze generously over the warm focaccia. Make sure every piece gets covered.
Set
Let the glaze set for a few minutes before serving.
Serve
Pull apart and enjoy! Each piece is like a mini caramel apple pie.