Use a strawberry huller, or just your clean fingertips, to remove the insides of the marshmallows. You don't want to squeeze too deep into the marshmallow or you'll tear through to the bottom of the marshmallow. Fingers or the end of a wooden spoon dipped in a bit of water helps even out the insides and makes things less sticky. I used a paring knife to smooth off the tops of the marshmallows once I was done. If you wish, set the marshmallow on top of a heatproof mug or bottle and lightly toast with a kitchen torch.