Preheat oven to 400 degrees F (if you're using dark metal pans, you might want to reduce this to 375-385 or reduce the baking time).
In the bowl of a stand mixer, combine cake mixes, eggs and oil and beat on medium until combined. The dough will come together quickly and pull away from the sides.
Roll cookies into 1" balls and place 2" apart on a lightly greased baking sheet or parchment paper. Bake for 7-8 minutes, until slightly puffed and tops look dry and set (don't worry -- the cookies will sink down as they cool). Set aside to cool completely.
In a small bowl, melt together the white chocolate and milk in the microwave in 30 second intervals on low heat. Set aside to cool to room temperature.
In the bowl of a stand mixer, combine puree, butter and vanilla and beat until smooth. Add chocolate and beat until combined.
Add the sugar, one cup at a time, and beat on low until combined after each addition. Add red or pink gel food coloring if desired. Beat on high for 2-3 minutes until light and fluffy. Set aside.
Combine puree, chocolate and milk in a small pot over low heat. Cook and stir over low heat until smooth.
Set aside to cool until it thickens to a spreadable consistency (if you let it cool too long and it becomes too thick, just heat on low again until you get the desired consistency)
Line 2 baking sheets with plastic wrap (I do this just so I don't have any mess to clean up!). Put half of the cookies on each sheet, with the bottom (or the inside of the oreo) facing up.
Spread or pipe frosting on all of the cookies on one baking sheet. Set baking sheet in the fridge while you do the other cookies (this helps the chocolate in the frosting to set so that the frosting doesn't all squish out when you sandwich them).
Spread ganache on all of the cookies on the other baking sheet. Remove cookies from the fridge and place one cookie from each sheet together, frosting and ganache to the inside.
If desired, roll in sprinkles or non-pareils. I like to store these in the fridge so the frosting stays nice and firm, but they also freeze incredibly well (and are great eaten frozen too!).
*If using frozen strawberries, thaw them first and make sure to drain any excess liquid.