Pulse the cookies in a food processor until fine.
In a bowl, mix the pulsed cookies with the melted butter and salt. Then, put 3 tablespoons of the mixture into each muffin tin.
Using your fingers or the back of a spoon, firmly press the mixture into the bottom and sides of the pan. Place in the freezer for at least an hour or until hard.
Use a knife to gently pop them out of the pan. Be careful as the sides can crumble a bit if they aren't very thick.
Keep them on a flat surface (like a baking sheet) in the refrigerator until you're ready to fill them.
To make the filling:
Fold the yogurt, cookie butter and gelatin together until smooth and combined.
Fill each tart with 1-2 tablespoons of the mixture.
Top with whipped cream, a drizzle of extra cookie butter (heat it in the microwave for a few seconds to make drizzling easier), melted chocolate or whatever else your tastebuds desire.
Serve immediately or store untopped tarts in the refrigerator or freezer in an airtight container.