Preheat the oven to 425°F Get out a 9"-diameter pie pan that's at least 1 1/4" deep. Or use a 9" to 10" cast iron skillet.
Coarsely chop the semi-thawed peaches; a few pulses in a food processor makes short work of this.
Mix the peaches with the remaining filling ingredients, stirring till thoroughly combined.
Roll half the crust into a 13" circle, and lay it in the pie pan or cast iron skillet.
Spoon the filling into the crust.
Roll out the remaining crust, and lay it atop the filling. Press the edges together, and crimp.
Brush the crust with milk, and sprinkle with coarse sparkling sugar, if desired. Cut several slits in the top, to allow steam to escape.
Bake the pie for 15 minutes. Reduce the oven heat to 350°F, and bake the pie for an additional 30 minutes, till the edge of the crust is brown. Cover the edge with a crust protector, or with strips of aluminum foil, to prevent over-browning.
Bake the pie for 15 to 20 minutes more, till the top crust is browned and the filling is bubbly.
Remove the pie from the oven, and allow it to cool completely, preferably overnight, before cutting.