Step one: set-up a water bath for the chocolates. Combine chocolates in a heat-proof bowl. Set the bowl over a saucepan of simmering water (do not let water touch bottom of the bowl), and stir with a rubber spatula until the chocolates have completely melted. The mixture should be smooth.
Step two: Remove bowl from the saucepan and stir chocolate mixture about 15-20 seconds to release excess heat. With a small spoon, carefully fill the candy cups with about a tablespoon of chocolate. Using the spoon or a pastry brush, brush the chocolate from the bottom of each cup up the sides to completely cover the inside of the cup. Gently tap the sheet pan on the counter to level the chocolate. Place the cups in the fridge to allow the chocolate to harden, about 15 minutes. Set the remaining melted chocolate aside.
Step three: Remove candy cups from the fridge. Using two spoons, fill each cup with about half a tablespoon of marshmallow creme. You can be as liberal as you want with the creme, just make sure it doesn't reach the top of the cup. It does get sticky, thus the use of two spoons. The creme will begin to spread out on the cup bottoms the longer it is kept at room temperature (this is ok). Then spoon a top layer of chocolate onto the marshmallow filling to completely cover it. Gently tap the pan again and place in the fridge to completely set about 20 minutes.