Place the flour in a bowl and make a well in the centre.
Whisk in the eggs and mustard, then gradually add the milk and salt to form a smooth batter.
Chill the batter in the fridge for at least four hours or overnight.
Preheat the oven to 220°C.
Heat a roasting tin containing 56g of beef dripping in the oven until hot.
Brown the sausages in a frying pan with the remaining beef dripping.
Whisk the chilled batter once more to combine.
Arrange sausages in the hot roasting tin and pour the batter over them.
Bake for 30 minutes, then release steam and bake for another 10 minutes.
Reheat the sausage pan on high heat and fry onions for 10 minutes until brown.
Stir in yeast extract and red wine, reducing the liquid by half.
Mix gravy granules with a little water, add 250ml water and beef stock, then simmer for five minutes.
Whisk in a knob of butter and season the gravy with salt and pepper.
Rest the toad in the hole for a few minutes before serving with gravy and peas.