Whisk flour, eggs, and mustard in a bowl until smooth.
Gradually whisk in milk and salt to create a smooth batter.
Chill the batter in the fridge for at least four hours or overnight.
Preheat the oven to 220°C.
Heat three-quarters of the beef dripping in a roasting tin in the oven.
Brown the sausages in a frying pan with the remaining beef dripping.
Place the sausages into the hot roasting tin and pour over the batter.
Bake in the oven for 30 minutes.
Briefly open the oven door to release steam and bake for another 10 minutes.
Simmer carrots in a pan with butter, salt, sugar, and 200ml of water for 4 minutes.
Boil the peas in salted water for 3 minutes, drain, and toss with butter.
Heat the veal jus and season with salt and pepper.
Serve the sliced toad in the hole with jus and vegetables.