My favorite way – and, in my opinion, the best way – is the method I used for the Devil’s Food Cupcakes. It gives you the maximum amount of filling and the best overall look for the cupcake. All you need is a paring knife, or other small, sharp knife with a narrow blade, to begin. Insert the knife into a cooled cupcake at an angle, halfway between the center and the outside edge.
The exact angle isn’t crucial, but it should be around 45 deg., and the knife should go into the cake about 1″. The idea here is to cut out a circular cone of cake.
Filling should be added using a pastry bag or (my favorite) a ziploc bag with the corner cut off. There is no need to use a pastry tip to fill the cupcakes; a medium-sized opening in either type of bag will make filling the cakes a breeze.
Once the filling is in place, just pop the flat circle of cake back into place and continue to frost as you would with any other cupcake. You can see what the finished cake, sliced in half to reveal the cream filling, looks like here.