Grease a 9x13-inch (23x33cm) baking dish with nonstick spray. Pour the white cake batter into the baking dish.
Bake for 25 minutes, or until the center is cooked through.
In a medium bowl, whisk together the peaches, condensed milk, and heavy cream. Use the whisk to break up the peaches.
Remove cake from oven and let cool for 30 minutes or until room temperature.
Once the cake is cool, use the rounded end of a wooden spoon to poke 6 rows of 5 holes in the cake. Tip: Clean off the end of the wooden spoon after every other hole to prevent making cracks in the cake.
Pour the peach mixture over the cake and use a spatula to spread it, filling all of the holes. Some of the mixture will stay on top of the cake. Chill in the fridge for 1 hour.
Remove the cake from the fridge and use a spatula to cover the cake in whipped cream. Then, arrange the peach slices on top in 5 rows of 11 slices.