In a large skillet over medium heat, add the sugar, water and raspberries. Cook until the sugar and the raspberries are wet and paste-like, about 8 minutes. Strain the mixture into a small bowl to remove the seeds. Line a small baking sheet with parchment paper. Spoon a little of the mixture, to form disks the size of a penny, onto the baking sheet. Freeze until hardened, about 2 hours.
To make the frozen bomb, using a 3 to 4-ounce ice cream scoop, put 8 full-sized scoops of ice cream onto a chilled platter. Next, remove the fruit disks from the freezer and from the bottom of the ice cream insert the fruit disk into the center of the ice cream. Continue this method until all are done. Return them to the freezer to set up nicely, this should take about 1 hour.
In a small saucepan, bring the cream and the butter to a boil over medium heat. Break up the chocolate into small pieces, add them to a stainless steel bowl and pour in the heated cream and butter mixture. Allow to stand for 5 minutes, then whisk until all the ingredients are well incorporated. Keep warm.
Remove the ice cream from the freezer. Stick a fork into the bottom of the ice cream and dip it into the melted chocolate to cover completely. Put the chocolate bomb on a wire cooling rack with a baking sheet underneath (to catch any dripping chocolate). Repeat with remaining ice cream and chocolate. Sprinkle with colored sugar or jimmies and return to the freezer.
To finish, cut the brownie squares in half, horizontally, making 8 squares. Using a cookie cutter, cut out circles a little bigger that the ice cream bomb. Arrange the circles on serving plates and top each with an ice cream bomb. Garnish with whipped cream, if desired.