Crush your cookies in a food processor until you have a fine crumb. If you do not have a food processor you can crush the cookies in a bag with a rolling pin.
Lightly grease tart pans
Mix the cookie crumbs with the melted butter until well combined.
Divide the mixture between the 6 tart pans and press the mixture into each pan. Make sure to take some of the crumbs up the sides of the pans. Use a greased spoon to really press the mixture into the pans. Let these sit in the freezer for 20 minutes to firm up
In a small saucepan (or the microwave), heat your cream until boiling. Once boiling pour it over the chocolate chips. Cover the bowl with foil and let sit for 5 minutes.
Whisk the cream and chocolate chips together. Add in the butter and continue to mix until butter is completely melted.
Pour the ganache into the chilled tart pans and let the tarts chill in the fridge for 2 hours until the ganache sets up.
Garnish with whatever you like!