Pre-heat your oven to 180°c (160°c for a fan-assisted oven or Gas Mark 4). Line a baking tray with greaseproof paper and set aside
In a bowl, mix the sausage meat and diced onion until it forms one mixture. I use my hands to incorporate the ingredients well
Roll out your puff pastry into one flat sheet. Lay the sausage meat into an inch width roll, and then roll the puff pastry round the sausage until the two layers of pastry overlap
Beat one large egg and one tablespoon of liquid (water, milk, or cream) in a small bowl with a fork until well combined. Brush the egg wash mixture evenly on the surface of the pastry using a pastry brush.
Bake in the oven for 25 minutes or until golden brown!