Preheat oven to 180 degrees. Grease a 6 cup muffin pan.

Spread the puff pastry squares into each of the hole. Allow to chill till the filling is prepared.

For making the toffee sauce, add the sugar and water into the pan and cook on low flame till all melted and caramelized. Add the butter, swirl in and switch off. Allow to cool.

Add the chocolate and cream into a bowl and microwave for 30 seconds. Whisk till smooth.

Beat the eggs with the vanilla for a minute with a whisk and add into the cream mixture, whipping till all incorporated and smooth.

Take out the chilled puff pastry tin. Divide the toffee sauce into each of the puff pastry and then top with the chocolate mixture.

Bake for 30 minutes. The puff pastry will look cooked and puffed, and the chocolate filling will puff up as well.

Cool in the pan for five minutes and slowly take out the tarts. Serve warm as is or with a dollop of ice cream or whipped cream.