Melt butter in a pan, add the apples, once it turns brownish, add in the coffee toffee apple jam and cinnamon, mix until fragrant.
lace a rack in the centre of your oven and preheat to 180 degrees C. Line an 8×8-inch baking pan with parchment paper so that the paper overhangs two sides like handles.
In a medium bowl, combine the oats, flour, brown sugar, ginger, and salt. Pour in the melted butter and stir until it forms clumps and the dry ingredients are evenly moistened. Set aside 1/2 cup of the crumble mixture, then press the rest into an even layer in the bottom of the prepared pan.
Scatter half of the apple filling over the crust. Sprinkle the cornstarch evenly over the top, then drizzle on the lemon juice and 1/2 tablespoon of the granulated sugar. Scatter on the remaining apples, and the remaining 1/2 tablespoon sugar. Sprinkle the reserved crumbs evenly over the top. You will have some fruit showing through.
Bake the bars for 35 to 40 minutes, until the fruit is bubbly and the crumb topping smells toasty and looks golden. Place the pan on a wire rack to cool completely.
White Chocolate Drizzle
In a medium bowl, melt the chocolate for 1 minute. Drizzle, slice, and serve.