Begin by preheating your oven to the temperature specified in your recipe process.

In a mixing bowl, combine the all-purpose flour, brown sugar, baking powder, and salt. Whisk these dry ingredients together until they’re well blended.

Add the cold, cubed unsalted butter to the flour mixture. Using a pastry cutter or your fingertips, work the butter into the dry ingredients until the mixture resembles coarse crumbs.

Incorporate the egg into the mixture, blending it thoroughly.

Slowly add the 1/4 cup heavy whipping cream to the mixture and mix until just incorporated.

Transfer about two-thirds of the prepared crust mixture into a baking dish, pressing it down firmly to form an even layer.

Bake the crust in the preheated oven until lightly golden or set.

While the crust is baking, prepare the creamy filling by mixing the sour cream, remaining heavy whipping cream, and powdered sugar in a separate bowl. Add the additional vanilla extract and whisk until smooth.

Once the crust has cooled slightly, pour the creamy filling over the baked base, spreading it evenly.

Gently fold in the diced peaches into the remaining crust mixture that was set aside and spread it evenly over the filling.

Return the layered dish to the oven and bake until the top is set and lightly browned.

Once baked, remove the dessert from the oven and allow it to cool completely in the dish on a wire rack.