Core strawberries with a small serrated spoon or knife and set aside. Combine mascarpone cheese, whipping cream, vanilla, and powdered sugar in the bowl of an electric mixer. Mix on high with a whisk attachment until cream starts to thicken and stick to the sides of the bowl. The cream should stick to the back of a spoon when done. Place cream into a large ziploc bag (or pastry bag) and cut a small opening in the corner with a pair of scissors. Pipe cream mixture into the center of each strawberry and set aside (I like to use a star tip on my pastry bag for this, but it's not required). Now it's time to melt the chocolate.