Red Velvet Cakes:

Preheat oven to 350° F / 176° C. Line a half-sheet rimmed tray with parchment, and set aside until ready to use.

In a large bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt.

In a separate mixing bowl or the bowl of a stand mixer, whip butter until light and fluffy.

Mix in the sugars, followed the egg and vanilla extract, mixing on high speed until well combined.

Add the red gel food coloring and mix until fully incorporated.

Fold dry ingredients into the batter, followed by buttermilk. Mix until just combined. Batter will seem very thick.

Transfer batter to a piping bag fitted with a 3/4-inch round tip. Pipe 1 1/2-inch rounds onto prepared tray, allowing space for the cakes to spread as they bake. With your fingertips, pat the tops of each cake to create a smooth, evenly domed surface.

Bake in preheated oven for 12 minutes, or until cakes are nicely risen and set around the edges, and spring back lightly when touched.

Repeat with remaining batter.

Allow whoopie pies to cool completely on the tray. Meanwhile, prepare the buttercream.

Strawberry Buttercream:

In a large bowl or the bowl of a stand mixer, whip the softened butter until light and fluffy.

Add the confectioner’s sugar, 1/2 cup at a time, mixing well after each addition.

Mix in the whole milk. If necessary, add a bit more milk or confectioner’s sugar to adjust the consistency. (The buttercream should be thick rather than runny or watery, but still thin enough to pipe with ease.)

Mix in the strawberry flavoring and pink gel food coloring.

Mix in the crushed freeze-dried strawberries.

Transfer to a piping bag.

Assembly:

Divide the cakes into pairs.

Pipe a generous blob of buttercream on the flat side of half of the cakes.

Top with the remaining cakes, using your hands to gently sandwich the two halves together.

Store leftover whoopie pies in an airtight container at room temperature for up to three days. If desired, whoopie pies can also be wrapped individually in clingfilm/plastic wrap.