Strawberry Crunch Sheet Cake

For Strawberry Crunch Topping:

Preheat oven to 250 degrees F. Line a baking sheet with parchment paper or a silicone baking mat.
In a mixing bowl, whisk together flour, sugar, milk powder, cornstarch, baking powder, and salt until evenly incorporated. Drizzle in melted butter and vanilla and mix until no dry ingredients remain; it should stick together into a crumbly dough.
Chill dough for 20 to 30 minutes (this makes it easier to crumble), then use your fingers to crumble dough onto prepared baking sheet, spreading crumbs into a single layer and breaking up any extra large pieces (ideally you want mostly pea-sized pieces).
Bake for 30 minutes or until just starting to turn light golden brown (they will crisp up more as they cool). As soon as you remove the baking sheet from the oven, use a spatula to lightly toss and break up the crumbs into smaller pieces where they’ve stuck together.
Separate out about 2/3 of the warm crumb mixture on the pan, and sprinkle this section with 2 tablespoons strawberry powder. Gently toss to coat crumbs evenly with strawberry. Sprinkle with remaining strawberry, and toss once more. Let cool completely, then mix the two colors of crumbs together to blend.
Crumbs can be made a few days ahead of time and stored in an airtight container at room temperature until ready to use.
For Strawberry Buttermilk Cake:

Preheat oven to 350 degrees F. Lightly butter a light or medium colored metal 13-by-9-inch baking pan, then line with parchment paper. If using a glass or dark-colored metal pan, decrease the temperature to 325 and bake for a few minutes longer.
In a bowl, whisk together flour, baking soda, baking powder and salt and set aside.
In a mixing bowl or the bowl of a stand mixer, beat butter for a minute or two until fluffy, then add sugar and continue to beat for 3 to 5 minutes or until very fluffy and aerated.
Add eggs, one at a time, mixing well after each and scraping down the sides of the bowl as needed.
Add half of dry ingredients, mixing on low speed until almost incorporated. Add buttermilk, oil, vanilla, Amoretti Natural Wild Strawberry Artisan Flavor, and red food coloring (if using), mixing until just incorporated. Scrape down the bowl again, then add remaining dry ingredients and mix until just incorporated.
Pour into prepared pan, spreading the batter into an even layer.
Bake for 18 to 22 minutes or until a toothpick inserted near the center comes out mostly clean with a few moist crumbs attached.
Let cake cool in the pan set on a wire rack while you prepare the frosting. You can also wrap the cake tightly in plastic wrap and refrigerate it overnight, or freeze for up to 2 weeks (ok to frost it while it’s frozen, just let it warm up to room temperature before serving).
For Buttermilk Frosting:

Combine cream, buttermilk, sifted powdered sugar, milk powder, salt and vanilla in a bowl, whisking until smooth.
In the bowl of a stand mixer, beat butter on medium-high speed for 5 to 7 minutes (seriously, that much) or until very pale white and fluffy.
With the mixer running on low, drizzle in about 1/4 of the cream mixture. Increase speed to medium-high and beat until fully emulsified and fluffy once again, another 2 to 3 minutes. Repeat with remaining cream mixture, 1/4 at a time. When all the cream has been incorporated, increase speed once more and beat for another few minutes or until frosting is very smooth, fluffy, and creamy. Reduce mixer speed to low for a minute or two to work out any air bubbles.
If the frosting seems greasy and not very fluffy, it’s likely your butter was too cold. Spoon about 1/2 cup of the frosting into a small microwave safe bowl. Microwave on 50% power for about 10 to 15 seconds or until just melted. Slowly drizzle melted frosting into bowl with mixer running on low speed, then increase the mixer to high and beat for 3 to 5 minutes. It should be nice and fluffy now. (You can also use this trick to ‘re-fluff’ buttercream that has been refrigerated, if you wanted to make it ahead of time for example. Let it sit at room temperature for an hour or so, then start mixing it as you pour in a small amount of melted frosting).
Conversely, if the frosting seems soupy and separated, your ingredients were probably too warm or you tried to incorporate them too quickly. Keep beating it, up to 5 or even 10 minutes, and it should come together eventually. You can also try chilling the entire mixing bowl in the refrigerator for 15 to 20 minutes, then beat it some more until it comes together into a light and fluffy buttercream.
Spread or pipe frosting onto cooled cake. Sprinkle with strawberry crunch topping, pressing lightly to adhere it to the frosting. Slice and serve at room temperature. Or refrigerate, covered or in an airtight container, for up to 3 days (let come to room temperature before serving).