Line two large baking sheets with parchment paper and preheat the oven to 350℉/190℃.
Sift together the flour, baking powder, and salt and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat together the butter and sugar on medium high speed for 2-3 minutes.
Add the eggs and vanilla and mix to combine, then add the strawberry powder.
Add half of the dry ingredients and mix on low speed.
Add a touch of food coloring (if using), then with the mixer running on low, add in all of the milk, and finally, the rest of the flour. Mix until just combined.
Use a 1.5 inch cookie scoop to scoop out the batter. Scrape it off on the side so the bottom is flush, and use a clean finger or paper towel to wipe off any excess batter from the sides of the scoop.
Add 6 dollops of batter to each cookie sheet.
Get a small bowl of water, dip your finger into it then gently press down all over the batter mounds to flatten them. Also pat around the edges to make as even of a circle as possible.
Bake the whoopie pie shells for 9-11 minutes or until you see no moist batter on the very tops. If baking two pans at a time, use the middle racks and switch pans at half.
Allow the whoopie pies to cool completely on the pan.