1 For the Yorkshire pudding batter, mix the flour smoothly with the milk, whisk in the eggs and season with salt and pepper. Add the thyme. Cover and put into the refrigerator for at least 2 hours.
2 Stand four Yorkshire pudding tins in a preheated oven (220°C) and let them get hot. Take out of the oven, divide 2 tbsp oil between them and return to the oven to heat the oil.
3 Meanwhile brown the sausages in the rest of the oil, then brush with mustard and place a sausage in the middle of each tin. Pour the batter around the sausages and return to the oven for 20-25 minutes, until golden brown and well-risen. Serve immediately.