Mix the flour, eggs and milk in a jug with 1/2 tsp salt, then set aside for at least 30 mins. Heat oven to 220C/200C fan/gas 7.
Untwist the links between each sausage, keeping them connected. Squeeze the meat to fill in the gaps, so you have one long sausage. Coil the sausage loosely and put in a large skillet or ovenproof frying pan (ours was 25cm wide.) Pour over the oil and brown in the oven for 12-15 mins.
Remove the pan from the oven and carefully lift out the sausage. Pour the batter into the pan, then put the sausage back on top, scatter with the herbs and return to the oven for 25-30 mins without opening the door – the Yorkshire pudding will sink if you do.
Meanwhile, heat the oil in a frying pan and cook the onions for 10 mins or until starting to caramelise. Stir in the flour and mustard powder and crumble in the stock cube. Stir in 500ml water bit by bit until you get a smooth sauce, then add the honey and mustard and season. Bubble for 5 mins, then serve with the toad-in-the-hole and mash and veg, if you like.