Put flour, eggs, milk and salt in a decent sized bowl and whisk, by hand, until the mixture is smooth
Spray 16 holes in a mini muffin tray with a decent amount of Low calorie cooking spray and place in the oven until it starts foaming slightly (5-8 minutes)
Divide the batter evenly between the 16 moulds and place in the oven
Cook for 8 - 10 minutes, or until they are crisp, golden and hold their shape
While you're waiting for the Yorkshire puds to cook, mix the horseradish and quark together
Place it in a piping bag fitted with a small star shaped nozzle
When the Yorkshires are cooked removed from the oven and allow to cool slightly
Pipe the horseradish mix into the hollow of each Yorkshire
Roll up each strip of beef and press them into the top of the Yorkshires puddings