In a food processor, add the cookies/biscuits and powder till fine. Transfer to a bowl
To this add melted butter
Transfer to the line pan, and pat it down to form a base. Make it even with the help of a spatula or the back side of a measuring cup.
Set aside. This is your base or the cookie crust
MAKE THE MOUSSE
Heat fresh cream, until it bubbles. Pour it on the chopped chocolate. Let it sit.
Use a spatula and mix. The chocolate will melt and form a thin consistency of ganache. Keep aside. Note : let the temperature of the ganache come down a little
In another large bowl, add cold whipping/heavy cream. Whip until stiff peaks
To the whipped cream, add the ganache. fold in gently so as to not deflate the whipped cream.Note: The ganache should not be completely set. it should still be pouring consistency. This ratio of chocolate and cream will not let the ganache set.
Fold until all of the ganache is completely mixed with no streaks of ganache
Now, layer this mousse on the cookie crust, and smooth the top with an icing/angled spatula.