Melt the chocolate over a double boiler or using the microwave (see instructions for either method in the blog post)
Stir the raspberry syrup into the melted chocolate
In a bowl, combine cream and vanilla, and using an electric mixer, whip until medium peaks form. (see blog post FAQ's for explanation) About 6-7 minutes.
Add melted chocolate mixture to the whipped cream and using a spatula, gently fold to combine.
Add 1 cup of the raspberries to the chocolate whipped cream mixture, folding gently to combine.
Divide the mousse into four dessert dishes.
Garnish each serving with the remaining raspberries and shaved chocolate if desired.