Set your oven to 350°F to preheat.
Combine the peach slices, sugar (1 cup), and salt (1/4 tsp) in a medium saucepan. Heat on medium for several minutes until the sugar dissolves, stirring occasionally. Remove from heat and set aside.
Dice the butter and place it in your 9×13 baking dish or cast iron skillet. Pop it in the preheated oven until the butter melts completely, then remove.
Mix the dry ingredients in a large mixing bowl: 1.5 c flour, sugar (1 cup), baking powder (2 tsp), cinnamon (1 tsp), and salt (1/4 tsp). Add the 3/4 cup milk and 1/2 cup (100 grams) sourdough starter to create a lightly sweetened sourdough biscuit dough. For best results, mix until just combined.
Pour the cobbler dough on top of the melted butter in your baking dish, but don’t stir—let the batter float on top of the butter. Spoon the cooked peaches and juice evenly over the batter. The batter will rise to the top of the fruit as it bakes, forming a delicious biscuit topping.
Place the cobbler in the oven for 35 minutes or until the top is golden brown and bubbly. The tender sourdough biscuits should have a fluffy texture and a crisp edge.
Enjoy your sourdough cobbler warm, topped with a generous scoop of vanilla ice cream.