• Preheat oven to 180C (350F). Spray a 9" x 13" baking dish with cooking spray. Set this aside.
• In a small mixing bowl or batter jug, combine the melted butter, eggs, vanilla, milk and sourdough starter and whisk until well combined. Now set the wet ingredients aside.
• In a large mixing bowl, combine the all purpose flour, baking powder, baking soda, sugar and salt. Stir them together until everything is well distributed.
• Now pour the liquid ingredients over the dry ingredients and whisk together to create the vanilla sheet cake batter.
• Pour the cake batter into the baking dish. Bake at 180C (350F) for approximately 30 minutes or until the cake is golden brown. It should stay fairly even while baking, but don't worry if it goes up in the middle, you can cut a little off to flatten it.
• Remove from the oven and allow the sheet pan cake to cool in the baking dish.

Vanilla Cream Cheese Frosting

• Add all of the frosting ingredients to the bowl of your stand mixer and beat on speed 8 until light and fluffy (this will take around 2 minutes). Alternatively, you can use a large mixing bowl and electric hand mixer.

  This vanilla cream cheese frosting is a double batch of the frosting featured in my sourdough cinnamon rolls recipe. It has a little extra powdered sugar to stiffen it a little.
• Once the cake has cooled, spread the frosting onto the cake and arrange the berries into flowers. Allow to sit for 15 minutes for the icing to set before slicing.