Preheat oven to 375° F. Grease a square 8" baking pan or line with parchment paper. Set aside.
In a medium mixing bowl, whisk together flour, sugar, baking soda, baking powder and salt.
Add melted/cooled butter and stir in with a fork. Reserve 3/4 cup of the mixture for crumb topping. Set aside.
Press the remaining mixture into the bottom of the prepared pan. Layer peach filling over crust. Stir reserved topping mixture with a fork until it resembles coarse crumbs. Sprinkle over the peach filling.
Bake for 20-23 minutes.
In the meantime, make glaze by whisking sifted powdered sugar with cream until drizzling consistency. Add more cream if needed.
When done baking, cool bars to room temperature in pan. When cool, cut and serve drizzled with glaze and scoops of ice cream.