Step 1
In a large bowl, toss peaches, sugar, cornstarch, and cinnamon until peaches are fully and evenly covered.
Step 2
Sift flour, sugar, and baking powder in a separate bowl. Add butter and combine with flour using a pastry blender or two butter knives until butter is pea sized and incorporated into flour mixture.
Step 3
Stir flour mixture until dough is shaggy and all loose flour and sugar are incorporated.
Step 4
Spray baking dish with cooking spray and add peach mixture.
Step 5
Add dollops of the topping to the top of the peaches until most of the baking dish is covered.
Step 6
Mix egg and 1 tsp of water and brush the topping with egg wash.
Step 7
Bake at 375F for 40-45 minutes or until golden brown. Let cool for at least 20 minutes before serving.