At your local cooking store, where they sell confectionery supplies, there are tiny metal cups, similar to cupcake tin liners. Also they sell silicone molds in many shapes, like hearts, spheres, holiday shapes, etc. Follow the directions on the product, but I would use a bit of baking spray to keep the chocolates from sticking.
Paint melted chocolate(I know we like milk chocolate...but don't do it....just use high cacao dark chocolate.) on the inside of the mold with a little paintbrush that you feel you can sacrifice for the cause.
This will make a thin shell. Pour a bit of Limoncello or your favorite liqueur into the resulting cup. Chill well
Now melt a bit of chocolate as high as you dare without burning it....it will burn at just a few degrees above body temperature. Pour the very liquid warm chocolate over the Limoncello in a very thin layer, and allow to harden. Pop them out of the mold and eat them alone!
If you have a mold that has a number of chocolates...Try laying the mold on a sheet of waxed paper, and pour a generous amount of the chocolate in a puddle at one end of the mold. Using a palette knife, gather a bit of the chocolate up on the knife and drag it over the entire mold like frosting a cake. leaving a thin layer of chocolate over the entire thing. Then go back while it is still warm, and scrape much of the layer off so there is a bit covering and sealing in the Limoncello.
You could also generously mix a liquor into your favorite butter cream frosting recipe, leaving out all other flavorings. Put a dab in each mold, freeze till firm, then flow chocolate over the opening.
You might drop in a tiny square of candied peel,an espresso bean etc., as well.
This will take tons of practice...I know this is an upsetting fact in view of the need to consume your mistakes.
Decorate your plain or chocolate frosted cakes with a few of these. How about hazelnut liquor filled chocolates, on a hazelnut cake with hazelnut butter cream!