For the mousse: Use the double boiler method to melt the chocolate. Fill a pot with approximately 2 inches of water and bring to a simmer over medium-low heat.
Place the chocolate in a heatproof bowl on top of the pot, making sure the bowl does not touch the water in the pot. Heat, stirring with a spatula, until the chocolate is melted, smooth and shiny. Allow to cool for 5 minutes.
Meanwhile, pour the cream into a bowl and whip with a handheld mixer until soft peaks form. Carefully fold the chocolate into the cream until fully incorporated. Add the mousse to a pastry bag or resealable plastic bag. Refrigerate for 30 minutes to set.
For the cookie bowls: Preheat the oven to 350 degrees F. Spray nonstick cooking spray into the cups of a 12-cup standard muffin tin.
Press about 2 1/2 tablespoons of cookie dough into each cup of the muffin tin, pressing the dough in the bottom and up the sides. Bake until the edges are golden brown but the centers are still soft, 14 to 16 minutes. If the centers of the cookie cups don't fall a bit when you remove the tin from the oven, use the bottom of a measuring cup or a small bowl to press the centers down. Cool in the tin for 5 minutes.
When ready to enjoy, pipe the mousse into each cookie bowl and top with berries and shaved chocolate if desired.