I used a Namaste GFCF chocolate cake mix (needs eggs) to make the chocolate heart cakes, but here is a recipe for chocolate cake that can be used for the whoopee pies. This is from the Feingold Blue Book.
1 1/2 cups of sugar (any cane sugar – I use organic from Costco or C&H)
6 TB cocoa (I use Hershey’s)
1 tsp salt (I use sea salt)
2 tsp baking soda
1 TB vanilla extract (watch for corn syrup)
3/4 cups of oil (I use organic canola or coconut oil)
2 TB Heinz white vinegar
2 cups of cold water
Combine the first five ingredients together in a bowl and mix. Add remaining ingredients. Stir until well combined. (Batter will be very thin.) Bake at 350 degrees for 40-50 minutes in a 9x13 pan or 20-25 minutes for cupcakes.
This filling is a little sweet for me but my kids loved it. There is another whoopee pie filling recipe that uses egg whites instead of marshmallow crème but you have to use a double broiler method to make it. That sounds too daunting for me.
Next time, we are going to try using chocolate frosting or strawberry frosting.
I may even have to try making the strawberry cupcakes in these pans. Pink hearts! That would be super cute. You could even use vanilla ice cream (365 brand from Whole Foods) to make ice cream sandwiches. Or you could use a yellow cake mix too to make little Twinkies. Oh, the possibilities! J
I think my kids are going to want these over plain old cupcakes from now on. These freeze really well too and thaw quickly. Place on a plate in the freezer for 30-60 minutes, then transfer to a large zip lock freezer bag.