Sausage & stuffing toad-in-the-hole with onion gravy

INGREDIENTS

• 140g plain flour
• 1 tsp English mustard powder
• 3 large eggs
• 300ml milk
• 4 tbsp sunflower oil
• 2 large onions , sliced
• 85g pack breadcrumb stuffing mix
• small handful sage leaves, chopped
• 8 sausages
• 2 tbsp plain flour
• 2 tbsp caramelised onion chutney
• 2 tsp Marmite
• 500ml beef stock