Combine flour, 1 tablespoon sugar, and salt in a bowl. Cut the chilled shortening and 3 tablespoons butter into small cubes and add to the flour mixture. Using a pastry cutter or your fingertips, work the butter and shortening into the flour until the mixture resembles coarse breadcrumbs with pea-sized pieces throughout—this creates a flaky texture. Add the ice-cold water a little at a time, stirring gently until the dough just comes together. Form into a disk, wrap in plastic, and refrigerate for at least 30 minutes while you prepare the peach filling.

Peel and slice the peaches into 1/2-inch wedges. Melt 1.5 tablespoons butter in a large pan over medium heat, then add the peaches, granulated sugar, brown sugar, cinnamon, nutmeg, lemon juice, and cornstarch. Stir gently and simmer for 8-12 minutes, stirring occasionally, until the peaches soften and release their juices and the mixture thickens. I like to mash about half the peach pieces with the back of a spoon to create a chunky-smooth texture—this gives the final ice cream better peach flavor distribution. Transfer the filling to a bowl and let it cool completely while you bake the crust.

Preheat oven to 350°F. On a floured surface, roll out the chilled dough from Step 1 to about 1/8-inch thickness. Brush the entire surface generously with melted butter, then sprinkle evenly with cinnamon sugar. Fold the dough in half, then fold again to create a layered effect—this creates those flaky, crispy bits you'll break up for topping. Cut the folded dough into 1-inch squares and spread them on a baking sheet. Bake for 15-20 minutes until golden brown and crispy. Once cooled, break the pieces into varied sizes—I prefer a mix of small crumbs and larger chunks for texture contrast in the ice cream.

Pour the very cold heavy whipping cream into a chilled bowl and beat with an electric mixer on high speed until stiff peaks form—this usually takes 2-3 minutes. Once peaked, gently fold in the sweetened condensed milk, vanilla extract, cinnamon, and nutmeg until just combined. Don't overmix at this stage or you'll deflate the whipped cream and lose the light, airy texture that makes this ice cream so creamy.

Gently fold the cooled peach filling from Step 2 and 1 cup of the baked crust pieces from Step 3 into the ice cream base from Step 4 using a rubber spatula. Work gently to keep the mixture light and airy. Pour the mixture into a 9x13-inch baking dish or similar container, then top with the remaining peach filling, drizzled over the surface, and scatter the remaining crust pieces on top. Freeze for at least 4 hours, or until firm enough to scoop. The ice cream will have a cobbler-like texture with pockets of soft peach and crispy crust throughout.