For the shortbread crust:

1. Preheat the oven to 350°F. Line a 13×9-inch baking dish with foil and grease the foil on all sides. In the bowl of an electric mixer, beat the butter until it begins to soften, about 30 seconds. Add the brown sugar and salt and beat on low speed until just combined.
2. Add the flour and beat on low until incorporated, then increase to high speed and beat until a cohesive dough forms.
3. Press the dough into the baking dish with your fingers and bake for 20 minutes, or until puffy and golden brown.

For the crumble topping:

1. While the crust bakes, whisk together the flour, brown sugar, cinnamon, ginger, and salt in a bowl. Drizzle in the melted butter and stir with a fork until large, clumpy crumbs form. Refrigerate until needed.

For the filling and assembly:

1. Spread the peach jam evenly over the hot crust, then layer with the sliced peaches.
2. Beat the cream cheese and sour cream on high speed until smooth. Add the granulated sugar and beat for another 30 seconds. Add the eggs and vanilla and beat until smooth and thoroughly combined. Pour the cheesecake mixture over the peach slices.
3. Scatter the chilled crumble evenly over the top.
4. Bake for 35–40 minutes, until the crumble is golden and the cheesecake is just set (it should have a slight wobble in the center). Cool completely before refrigerating. Chill for at least 2 hours before cutting into bars.