Prepare the Butter: Cook cold unsalted butter in a stainless steel pan over medium heat for 10-12 minutes until it reaches a medium brown color. Chill in the freezer until firm, about 1 hour.

Cube the Butter: Cut the chilled browned butter into cubes and keep them in the freezer.

Mix the Dry Ingredients: In a stand mixer, combine the flour and salt. Add the cubed butter and mix on low speed until resembling pea-sized pieces.

Make the Dough: Combine water and vinegar with ice, then gradually add to the flour mixture until clumping. Divide into two rounds, wrap in plastic, flatten into discs, and chill for at least 1 hour.

Preheat the Oven: Set oven to preheat at 425°F.

Roll Out the First Disc: Roll one disc to ⅛ inch thick, place in 9-inch pie pan, and chill.

Prepare the Lattice: Roll the second disc, slice into strips, and chill on a parchment-lined tray.

Mix the Filling: Combine peaches, strawberries, sugar, lemon juice, zest, cornstarch, and salt in a bowl. Pour into the prepared pie crust.

Assemble the Lattice: Arrange lattice over the filling, tuck edges, crimp to seal, and brush with whisked egg. Sprinkle turbinado sugar if desired.

Bake the Pie: Place on a baking sheet and bake for 25 minutes, then lower temperature to 350°F and bake for another 40-50 minutes, covering with foil if necessary.

Cool Before Serving: Allow pie to cool for at least 4 hours before serving.