Tagalongs Girl Scout Cookie Mousse Cake

Line a 9- by 5-inch loaf pan with plastic wrap, making sure the plastic is tucked into the corners and leaving at least a 2-inch overhang on all sides.
In a dry metal bowl set over a pan of barely simmering water, melt the chocolate, stirring until smooth. Let cool slightly.
Spread a small amount of melted chocolate on the rounded side of 9 cookies and place 3 of them, chocolate side down, on the bottom of the pan, in a row. Place another 3 cookies against each long side of the pan with the chocolate-coated sides facing the pan. Place the pan in the freezer.
In a small saucepan over low heat, combine the peanut butter chips with 1 cup plus 2 tablespoons of the heavy cream. Warm, stirring frequently, until the peanut butter chips are just melted. Remove from the heat and continue to stir until the mixture is smooth. Add the peanut butter and the vanilla and stir until incorporated.
In a stand mixer fitted with the whisk attachment, combine the remaining 1 1/2 cups heavy cream with the sugar and beat until the cream is very thick but not yet holding peaks. Add the whipped cream to the peanut butter mixture in 3 additions and fold in just until the mousse is streak-free.
Carefully spoon about 3/4 of the mousse into the prepared pan, being careful not to move the cookies. Insert the remaining cookies into the mousse, arranging them in a row down the center of the loaf pan. Spread the remaining mousse over the wafers and carefully smooth the top. Press plastic wrap directly on the surface of the mousse then wrap the entire pan in a double layer of plastic wrap and chill until firm, at least 1 hour or overnight. DO AHEAD: The mousse cake can be made ahead, wrapped in a double layer of plastic wrap, and chilled for up to 3 days.
To serve, take the mousse cake out of the refrigerator and remove the double layer of plastic wrap, along with the plastic wrap pressed on the surface of the mousse. Using the overhanging plastic wrap that lines the pan, carefully lift and loosen the cake from the pan without removing it. Place a large plate or platter on top of the pan then invert the cake and the plate. Remove the pan and the plastic wrap and serve immediately.