Roll out the pie crust, and cut circles in it. Put them on a plate and in the fridge for 1 hour.
The caramel : Put the sugar in a pot at medium heat. Leave it melt and caramelize, shaking the pot sometimes to stir.
Once the caramel has formed, add the butter at once (be careful of the splashes). Mix well.
Then pour the cream, and mix until the caramel is melted. Bring to a boil, then thicken it during 10 minutes, stiring regularly. The caramel will be still liquid, but it will get thicker once it has cooled down.
Turn your muffin mould upside down. Place the crust circles on it.
Bake 15 minutes at 350°F (180°C). Leave to cool down, and unmould.
Fill them with caramel (if it is too hard, put it in the microwave for a few seconds). Put the tarts in the fridge for 1 hour.
Melt the chocolate and pour some on each tart. Rotate them to spread evenly the chocolate on top of it. Put back in the fridge for 1 hour.
There you are, your caramel and chocolate mini tarts are ready!