Preheat the oven to 200°C/400°F/gas 6 and line a 35cm x 25cm baking tray with baking paper.
Unroll the puff pastry onto a lightly floured surface, with the short edge in front of you.
Beat the egg in a small bowl, then brush liberally all over the pastry. Finely grate over the cheese and sprinkle with the poppy seeds.
Carefully cut the pastry into 12 long strips and twist each piece into a spiral, placing on the prepared baking sheet as you go.
Flatten both ends of each strip to make a head and tail, then decorate with the pumpkin seeds to make eyes and a tongue. Try shaping and bending a few of the strips to make the snakes look like they are slithering around!
Carefully transfer the tray to the oven and bake for 12 minutes, or until crisp and golden. Delicious served with Roasted pumpkin houmous.