Step A: Make some cake balls! I have a nifty little cake ball maker that just does it on my stove top (it's like a waffle iron almost, except it makes little balls of goodness!). I just used that for the first layer. Do whatever color/flavor/WHATEVER you want! My test batch used a Funfetti cake mix that I used some pink gel food coloring to turn SUPER pink! SQUEE! Make the box. Or half a box. Or whatever. Just keep in mind that you'll be using about 2-3x the amount of the outer cake batter that you use for cake balls. If you want to go for old school cake balls, you know, the "I'd like a little cake with my frosting" cake balls, by all means, do it! Just keep in mind that it may lose it's shape a bit when baking because the frosting could melt. Also, be sure to not over bake them, they'll be baked again! It's perfectly acceptable in this case to have slightly under baked cake balls.
Step B: Prepare your outer cake batter. For mine, I used red velvet. Line a cupcake pan with the liners you desire. Put a small amount of your second batter on the bottom. Don't go overboard! It'll bake up, and push your cake ball up through the top of the pan. You just want to hide the bottom of the cake ball is all. Press a cake ball into the batter. Cover the cake ball with batter! Don't fill the cups too full though, remember, the batter will rise up. Bake about 2/3 what the box or recipe says to, then check to see if they are done by inserting a toothpick near the EDGE of the cupcake. Your cake balls in the center are already done, so you're just testing the batter around them. When the toothpick comes out clean, they're done! Take them out, let them cool, and then frost however you like. Mine, I put a pretty little swirl of cream cheese frosting on top.
Want to see the insides? It's pretty cool! Also, I promise that the insides were far more pink than my camera shows.
I figure that for the gender reveal party, I'll do my Lemon cupcake (yellow is nice and neutral, and who doesn't like lemon?!) with a blue or pink cake ball inside! Alright folks. Tell me how you plan to make this work for you! Chocolate cake ball in a butter cake? Neon green mint inside a chocolate cupcake?