One of the best tricks candy makers perform is putting a liquid center inside of a chocolate shell.  These chocolate pieces are not only fun and satisfying, they are also quite delicious— especially if you love liqueur!
There are a couple of ways to achieve a liquid center inside of a chocolate shell.  First, a candy maker can use a fondant with invertase , as in a cherry cordial. Second, a candy maker can cook a sugar mixture to a thread stage (230F) add liqueur, and create a sugar shell that can be coated in chocolate.
For a cherry cordial, we create a fondant (a pasty mixture of sugar, glucose and water) and dip the cherries into the mixture. Invertase (an enzyme) is added and the fondant around the cherry liquifies over time as they cure in their chocolate shells.
A cordial made with crystallized sugar requires a truly unique technique. They are created by using a method of starch molding. A syrup mixture is cooked to a relatively low temperature a mixed together with a sprit. Over time, the mixture crystallizes, encasing a liquid center. 
Photo: Commercially produced key lime cordials.
Recently, I was asked to make some of these types of candies as a special addition limited time offering for the chocolate case.
 I started by fitting a full size sheet pan with an extender. I filled it with corn starch and leveled it off using a tool I created out of wood and clay —a board with baked clay designs including heart shapes and moons. Next, I pressed designs into the starch. This took some practice. It was tough to achieve clear defined shapes. Yet after awhile I got much better at pressing in the designs.
Photo: Shapes made in corn starch. 
Photo: Wooden tool used to shape the hearts. 
Next, I cooked a simple syrup mixture to the thread stage —230F it consisted of 2 1/4 cups sugar and 1/2 cup of water. As soon as the mixture reached temperature, I took it off the heat and poured it into another pot to arrest any carry over cooking. I then added 1/3 cup of Grand Mariner. I carefully mixed the cognac together with the syrup by gently pouring back and forth between to pots. When the mixture had cooled (about 5 minutes), I poured off into a squeeze bottle and carefully filled the cavities.
Photo: Grand Marnier -- gettin' boozy. 
Photo: Filled in cavities.
I allowed the pieces to cool longer and sifted additional starch over the top. 
The next day, I had crystallized sugar pieces with a liquid center I could dip into chocolate. 
Photo: Crystallized sugar hearts. Ready for dipping!
Photo: Chocolate coated liqueur cordials with gold flecks. 
These chocolates were great! They produced a nice taste of liqueur encapsulated in a crystallized sugar. The chocolate (milk or dark complimented them very well. 
Photo: A cut-open Chocolate Liqueur Cordial.