Preheat the oven to 200°C, 180°C fan, Gas Mark 7
Put the sausages in a relatively deep oven proof dish (your Yorkshire Pudding is going to rise to epic proportions!), with a little oil, and bung them in the preheated over for 20 minutes
Add the thyme leaves and the mustard powder to the Yorkshire Pudding batter and mix in
Whilst the sausages are cooking add the sliced onions to a little oil in a pan and cook very gently until they have softened and are golden but not browned. (This is going to take at least 20 minutes, so don't expect it to be quick!)
After 20 minutes, take the sausages out of the oven, turn them over and add the Yorkshire Pudding Batter. Get it back in the oven as quickly as you can to avoid letting the oil cool. Bake for 30-40 minutes until the Yorkshire Pudding has risen to levels you have never seen before!
When the onions are ready, add the sugar and cook for another 5 minutes before adding the flour. Stir the onions until all the onions are coated in the flour.
Gradually add the stock stirring all the time. Once you have added all of the stock let it cook for about 5 minutes until the gravy has thickened.
Pour the gravy over the toad in the hole and serve