While trying to keep the stem intact, pit the cherries. Set aside. A cherry pitter makes this job effortless.
Add the mascarpone, powdered sugar, and heavy cream into a medium sized bowl. Use a hand mixer to cream all of the ingredients together. Transfer the mixture into a piping bag.
Pipe the mascarpone mixture into the holes in the cherries and then place them on a plate. When all of the cherries are filled, transfer them into the freezer for 30 minutes.
Line a plate or small cookie sheet with parchment paper. Set aside.
In a microwaveable bowl, add the chocolate chips and butter. Melt the chocolate using 30 second intervals until completely melted.
After the cherries have set in the freezer, cover them in chocolate. Hold the stem of the cherry and dip the filled cherries into the melted chocolate. If the stem has broken off the cherry, use a toothpick. Roll the cherry around in the chocolate until completely coated in chocolate. Place the cherries on the lined cookie sheet or plate.
Refrigerate the cherries for at least 20 minutes before serving to allow the chocolate to set.