Make the Strawberry Reduction: Start by pureeing ¾ lbs of fresh strawberries with a food processor. Afterwards, you should be left with about 1 cup of puree. Place the strawberry puree into a saucepan over medium-low heat and simmer for 30-35 minutes, stirring occasionally. When you’re done with the reduction, you should have about ½ cup (if you have more, keep cooking!). Place the reduced puree into an airtight container and refrigerate it for at least 30 minutes, or until it reaches room temperature. Then, whisk it together with the whole milk and set aside.

Preheat the oven to 350ºF and prepare a 13x9 inch cake pan or casserole dish by spraying the sides with cooking spray and lining the bottom with parchment paper.

In a medium bowl, add the sifted cake flour, baking powder, baking soda, and salt. Whisk to combine and set aside.

In the bowl of your stand mixer with the paddle attachment, whip the butter on high until creamy, 2 minutes. Add the granulated sugar and beat together with the butter at medium speed for 2 minutes, until light and fluffy. Turn the mixer to low and add the eggs one at a time, making sure each one is incorporated before adding the next. Add the vanilla and sour cream, then turn the mixer to high and beat for 1 minute.

Keeping the mixer on low, add all of the dry ingredients at once until just combined, then add the strawberry milk mixture and pink food coloring (if using) until just combined, about 30 seconds. Give the batter a few stirs by hand to make sure everything is incorporated without over-mixing. Pour the batter into the prepared cake pan and use a spatula to smooth the batter down evenly and spread it into all four corners.

Bake the cake for 35-40 minutes, until a toothpick inserted comes out with just a few moist crumbs. Let the cake cool completely before frosting.

With a food processor, grind the freeze-dried strawberries into a fine powder and set aside. You'll have between ¼ and ⅓ Cup of strawberry powder after grinding.

Whip the butter using a stand mixer with a paddle attachment on medium speed until it’s creamy and light in color (5-10 minutes). Add vanilla, milk, and strawberry powder and continue to mix on medium for 1 minute.

Add the powdered sugar a few cups at a time, scraping down the bowl and paddle after each addition. Add the salt and mix on low for another 30 seconds.

To create the look pictured, reserve about 1 Cup of strawberry buttercream before frosting the (cooled to room temperature) strawberry sheet cake with the remaining strawberry buttercream. Use an angled spatula to create rustic texture in the frosting finish.

Divide the reserved strawberry buttercream between two piping bags, one fitted with Wilton Tip 1M and one fitted with Wilton Tip 4B. Use the bag with Tip 1M to pipe rosettes along the edges of the cake, focusing mostly on two opposite corners. Use the bag with Tip 4B to pipe clusters of stars around the rosettes. Garnish with fresh strawberry slices and chamomile flowers.