First, make the chocolate cake. Position a rack in the center of the oven and preheat the oven to 350°F. Generously spray an 8 x 8-inch square pan with cooking spray and line the bottom with parchment paper. Spray the parchment, too.
In a medium bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
In a large bowl, whisk together the buttermilk, oil, eggs, and vanilla. Gradually whisk in the dry ingredients until just combined. Slowly pour in the coffee. The batter will be fairly runny; use a rubber spatula to scrape down the bottom and sides of the bowl. Use the rubber spatula to finish mixing until smooth and well combined, 2 to 3 minutes more.
Pour the batter into the prepared pan and use an offset spatula to smooth its top if necessary.
Bake the cake. Bake for 30 to 35 minutes. When done, the top of the cake should bounce back when gently pressed and a skewer inserted into the center of the cake should come out with a few crumbs attached. Cool completely in the pans on a wire rack before frosting. Once the cake is cool, make the strawberry cream cheese frosting. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, cream cheese, and vanilla on medium-low until soft and creamy, 2 to 3 minutes. Scrape down the bottom and sides of the bowl with a rubber spatula. With the mixer on low, gradually add the confectioners' sugar, freeze-dried strawberries, and salt and beat until combined. Scrape down the bottom and sides of the bowl once more, then beat on medium-high until the frosting is creamy and smooth, 2 to 3 minutes. Assemble the chocolate strawberry snack cake. Use an offset spatula to cover the top of the cake with the frosting completely. Garnish with sprinkles.
Serve and store. Serve at room temperature. The cake will keep in an airtight container for 1 day. After that, transfer to the refrigerator and refrigerate for up to 2 more days.