Roll out the puff pastry to ⅛ in/0.3 cm thick. Using a pizza wheel, cut into 3¾-in/10-cm squares. Cut the squares in half on the diagonal to make even triangles.
Using a small paper cone, pipe a pea-size dot of mustard onto each triangle.
Cut the cheese and ham into 3½-in/9-cm batons. Place one cheese and one ham baton down the middle of each triangle