- Make the filling: Preheat oven to 350 degrees. In a large bowl, gently toss peaches, sugar, lemon juice and zest, and spices until evenly coated. Transfer filling to a deep cast-iron pan or 8×8-inch baking dish. Place pan on a sheet tray and bake until filling is bubbling around the sides, about 35 minutes. Using a wooden spoon, carefully mix the filling, scraping down the sides, without breaking up peaches.
- Make the topping: In a medium bowl, whisk flour, sugar, baking powder, and salt until thoroughly combined. In a separate bowl, whisk buttermilk, butter, and vanilla. Slowly whisk buttermilk mixture into flour mixture until smooth with no visible clumps. Pour batter over the filling (don’t worry about making an even layer), using at least half the batter or all of it for a thicker topping. Return pan to oven and bake until golden brown, 35 to 40 minutes. Remove and cool pan on a wire rack for at least 10 minutes.
- Make the milk dip: In a medium saucepan over medium heat, whisk together milk, sugar, cornstarch, and salt. Bring to a boil, whisking constantly to prevent scalding. Reduce heat to a gentle simmer and cook, uncovered, until mixture is reduced by half and thickened, about 15 minutes. Remove from heat and pour through a fine mesh strainer, then whisk in vanilla paste. Transfer milk dip to a pourable container and set aside until ready to use. Serve sonker with a generous pour of milk dip over top.
From Cobbler & Co.