Heat up a large saucepan or frying pan up over a medium heat. Add in half the cooking oil plus the chicken and leeks. Gently fry until the chicken is browned on all sides.

Add in the spring onions and the marjoram. Add the remaining oil. Stir and fry for another minute. Once the chicken is almost cooked right through add in the chopped garlic and season well with salt and pepper. Turn down the heat. Fry the garlic for around 20 seconds until fragrant.

Crumble in the stock cube then pour in the water. Stir until the stock has dissolved. Add the mustard and stir gently once more. Bring to a gentle simmer.

Cook at a gentle simmer until the water has reduced down by around 2/3rds and the chicken is nice and tender. Remove from the heat and allow to cool for around 2 minutes. Add in the quark and stir through until no lumps remain and a creamy sauce is created that coats the chicken.