Heat oven to 400° F.
Cut the sausages in quarters lengthwise, then in half crosswise.
Cut the puff pastry into strips 3 inches long and 1 inch wide. Roll the sausage pieces in the pastry strips and transfer to a parchment-lined baking sheet.
Bake until puffed and golden brown, 15 to 20 minutes.
Transfer to a platter and serve with the mustard for dipping.