Lancashire Hotpot Hasselback Potatoes

Name: Lancashire Hotpot Hasselback Potatoes
Cuisine: European, British
Ingredients: 50g dripping or butter, plus extra to grease; 900g best-end or middle-neck lamb, cut into large chunks; Flour, seasoned with salt and pepper; 1 tbsp worcestershire sauce; 2 sprigs of thyme, leaves picked; 1 bay leaf; 2 onions, sliced; 500ml lamb stock; 200g new potatoes