Pulse the cookies in a Cuisinart until fine.
Mix them 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. Then use a knife to gently pop them out of the pan (just 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, simply fold the yogurt, cookie butter and gelatin together until smooth and combined.
Fill each tart with a tablespoon or two 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.