I'm familiar with making these from my days working with a Swiss chocolatier.
First he would fill 2 hotel pans about 2 inches deep with cornstarch. Then he would place these pans under our deck ovens for about 3 weeks, sifting them every day to dry them out. Next, he'd boil sugar and water to a certain sugar density read by a density meter and add liqueur, then cool. Then the cornstarch was sifted again and spread in an even layer and impressions were made in the cornstarch with a ceramic mold. The cooled syrup was then poured into each impression and more cornstarch sifted over the top. After drying for about 24-36 hours the candies were carefully lifted out and the excess cornstarch was brushed off. They were then dipped in tempered chocolate. This part was really tricky as the sugar shell was very fragile and broke easily, ruining the chocolate.
Overall, these are very difficult to make. The drying process is very important because if the cornstarch contains too much moisture, the impression will not hold and the syrup will run. I don't have the correct sugar density reading anymore and have not seen the density meters available anywhere, nor do I have the ratio of sugar syrup to liqueur. The results were lovely, but it's a confection that might be best left to the experts.