Crimp the border using your thumb and forefingers, or the blade of a cutlery knife, pressing it around the edge to seal (flour the knife if it starts to stick). Brush more of the beaten egg all over the wellington. If you like, stamp out decorations from the pastry offcuts using biscuit cutters (or cut out using a knife), then fix these to the wellington using some of the beaten egg. Alternatively, simply score the top using a sharp knife. Cover and chill for at least 1 hr, or for up to 48 hrs. At this stage, you can freeze the wellington for up to two months. Defrost completely in the fridge before baking. When you’re ready to cook, heat the oven to 200C/180C fan/gas 6.
