Preheat your oven to 425°F (220°C) and pour the vegetable oil into a 9x13-inch metal baking dish or a large cast-iron skillet.

Place the pork sausages into the oiled dish and bake for 10 to 12 minutes until they are lightly browned and the oil is sizzling hot.

While the sausages are in the oven, whisk together the flour, eggs, milk, and salt in a large bowl until the batter is completely smooth and free of lumps.

Carefully remove the hot dish from the oven, then immediately pour the batter over and around the hot sausages while the oil is still smoking.

Return the dish to the oven right away and bake for 25 to 30 minutes until the batter is puffed up, crisp, and beautifully golden brown.

Do not open the oven door during the first 20 minutes of baking, or the Yorkshire pudding batter may deflate and lose its airy texture.

While the pudding bakes, melt the butter in a saucepan over medium heat, add the sliced onions, and cook for 15 minutes until soft and caramelized.

Pour the beef stock into the caramelized onions, bring to a gentle simmer, and let the mixture reduce for 10 minutes until a rich, glossy gravy forms.

Cut the freshly baked Toad in the Hole into generous portions and serve immediately alongside steamed vegetables and the warm onion gravy.