To make the pastry crust, grate butter into flour and toss together. Add shortening and mix lightly with your fingertips. Stir in sugar and salt, and mix.
Add ice-cold water and egg yolk and mix gently to bind into a fine and smooth dough. Wrap in plastic and refrigerate for 30 minutes.
Divide dough into equal portions and press each portion evenly over the base and sides of small tart moulds. Bake blind at 180°C for five minutes; remove beans and continue to bake for seven to eight more minutes.
To make the filling, cream the cheese, butter and sugar until light. Add eggs one at a time. Stir in milk and sift in corn flour. Add whipping cream and stir well to mix. Spoon filling into tart moulds.
Bake in a preheated oven at 180°C for 25 minutes. Halfway through baking, add blueberry filling on top of the tarts as a decoration and continue baking.
Remove from the oven and cool completely, then refrigerate until the tarts are well-chilled before serving.