Make a suet crust pastry. Roll out into a square and lift on to a piece of greased parchment paper. Open the mussels by heating gently in a dry, covered pan. Remove beards. Scoop them out on to one half of the dough, leaving an edge free all round. Season. Damp this edge and fold the pastry over, covering the mussels. Press the edges of the pastry ‘envelope’ together. Tie up in a cloth and steam for one and a half hours.