Preheat the oven to 350 degrees F. Melt the 1 tablespoon of butter in a 10-inch cast iron skillet over low heat spreading it out to cover the bottom of the pan. Turn off the heat.
In a large mixing bowl, toss the peaches with the sugar and cornstarch until everything is well combined. Set aside.
Prep the Topping, Assemble, and Bake
Whisk the flour, sugar, baking powder, cinnamon, cardamom, and kosher salt together.
Add the cold cubed butter to the flour mixture. Using your hands, a fork, or a pastry cutter, cut the butter into the flour until coarse pea-sized pieces have formed.
Whisk the egg into the milk and then pour the mixture over the flour and butter. Mix everything together with a fork until well combined.
Dump the peaches and their juices into the cast iron skillet. Spread them out into an even layer.
Spoon the batter on top of the peaches and spread it out to cover most of the top. Note: the batter won't cover all of the peaches but it will expand as it bakes to cover most of them.
Sprinkle the top of the batter with turbinado sugar (optional) or granulated sugar.
Bake for 40 minutes or until the top is lightly golden brown and the edges are bubbling.
Cool for about 20 minutes before serving. Serve the cobbler with vanilla ice cream.
Notes
Store the cobbler in an airtight container in the fridge for up to 4 days.Reheat in an oven-safe dish at 350 degrees F for about 10 minutes or until warmed through.