- STEP 1
Whisk the flour, eggs and milk together with a pinch of salt until smooth. Cover and rest for 30 mins (or chill in the fridge overnight).
- STEP 2
Heat oven to 220C/200C fan/ gas 7 and put a large pan of salted water on to boil. Heat the oil in a large roasting tin (40cm x 30cm approx) in the oven for 10 mins. Once hot, pour in the batter and cook for 25 mins or until puffed up and golden.
- STEP 3
Meanwhile, tip the peas and kale into the boiling water and cook for 2-3 mins until tender. Drain well and season.
- STEP 4
When the pudding comes out of the oven, remove from the tin, flatten with the back of a large metal spoon and halve lengthways. Spread 1 tbsp horseradish over each half, followed by the mustard, beef slices, peas, kale and gravy. Wrap up and serve.