Heat oven to 200C/180C fan/gas 6 and pop a baking sheet inside to warm. Mix together the sausagemeat with the chipotle paste, chilli, onions, coriander, lime zest and juice and a little seasoning, before squashing in the kidney beans.
Unroll the pastry onto a sheet of baking parchment, longest side towards you, and spread the sausage mixture down the centre of the pastry – it should make a rounded mound about 10cm wide.
Measure 1cm out from the filling, then cut the sides of the pastry on a slight diagonal into 1.5cm thick strips. Lift these up and over the sausage filling so that they meet on top. Use the last pieces to wrap up the ends. Brush with the egg and sprinkle on the oregano, if using.
Using the baking parchment, carefully lift the sausage plait onto the hot baking sheet and bake for 40 mins until golden and cooked through. Serve with ketchup and a green salad, if you like.