Preheat oven to 350°F. Prepare 12 in. x 18 in. jelly roll pan with parchment paper.
In large bowl, sift together flour, cocoa powder and salt.
In large bowl, beat butter and sugar with electric mixer until light and fluffy. Add eggs, vanilla extract and icing color; beat until well combined. Alternately add flour mixture and buttermilk in three additions, beating until just combined. Stir baking soda into vinegar; fold carefully into batter (do not beat). Pour into jelly roll pan and smooth with spatula.
Bake 25-28 minutes or until top of cake springs back when touched. Cool completely on cooling grid. Remove from pan onto flat surface. Remove parchment paper. Cut 36 circles using the 1-1/2 in. small circle cutter*.
For icing; beat butter and cream cheese in large bowl with electric until light and fluffy. Add vanilla. Gradually add confectioners? sugar, 1/2 cup at a time. Beat on high until smooth; add milk and mix well.
If icing is too thin, add confectioners? sugar 1 tablespoon at a time. If it is too thick, add more milk 1 teaspoon at a time until icing reaches desired consistency.
To assemble: Place one cake round in bottom of treat pop. Pipe a swirl of cream cheese icing from back edge following the curve of the container, then filling in the center. Continue layering until treat pop is full. Top with a swirl of cream cheese icing and red colored sugar.
*Tip: Use the small (1-1/2 in.) round cutter from the Wilton 101 Cookie Cutter Set.