Preheat oven to 200°C. Line 2 oven trays with baking paper.
Heat oil in a large frying pan on medium. Saute onion and garlic for 3-4 minutes, until tender. Stir in mustard, cumin and fennel. Cook 1 minute, until fragrant. Cool.
In a large bowl, combine onion mixture with pork, breadcrumbs, parsley and egg. Season to taste and mix well.
Divide pork mixture into 4 even pieces. Shape pork into 20cm sausages.
Place 1 sausage along each pastry strip. Brush one side with a little extra egg (or milk) and roll up to enclose, pressing to seal. Slice on an angle into 4cm slices and place, seam side down, on tray.
Brush with egg and sprinkle with seeds. Bake for 25-30 minutes, until pastry is golden and puffed. Serve hot with tomato chutney.