Lightly spray your candy mold with coconut oil cooking spray.
Combine chocolate and butter in a double boiler over medium heat, stirring constantly for about 5 minutes, or until the chocolate begins to melt.
Once the chocolate is quickly melting, reduce the heat to low. Continue stirring for 2 to 3 minutes.
Mix milk into chocolate with a rubber spatula, 1 tablespoon at a time, until it is thoroughly combined and the chocolate is smooth and easy to pour (about 3 to 5 minutes).
Remove mixture from heat and immediately start spooning chocolate into molds. Be sure to push chocolate into any crevices of the mold. If you wish to add filling, then fill molds only halfway.
If using, add miniature marshmallows, pecans, coconut, or other filling choices to the middle of the chocolate mold. Top the rest of the mold with chocolate. Level the back with a butter knife.
Place mold in refrigerator and chill for at least 4 hours before serving.