Mash, gravy & bangers

Ingredients

• 8 sausages
• 2 onions, sliced
• ½ tsp dried mixed herbs
• ½ tsp mustard
• 600 ml beef stock
• Salt and black pepper
• 2 tsp softened butter
• 2 tsp plain flour
• 900 g potatoes, peeled and chopped into equally sized cubes
• 50 g butter
• 100 ml milk
• 2 tbsp English mustard