Half cover pumpkin with salted water and bring to the boil. Cook for about 8 minutes until tender. Drain. Mash with half the butter until smooth. Season well with salt & pepper. Keep warm.
Spread mustard over both sides of pork. Season with salt and pepper.
Heat an oiled, non-stick frying pan over a medium to high heat. Add pork. Cook for about 3 to 4 minutes on each side, or until cooked. Transfer to a plate.
Add a dash of water and remaining chopped butter to same hot pan. Stir until melted and almost simmering. Remove pan from heat. Stir in lemon juice. Return pork and any meat juices to pan. Turn to coat.
Put a little salted water on to boil, add the beans and broccolini and cook for 4 minutes until just tender. Drain
Serve pork with pumpkin mash, beans, broccolini and lemon wedges. Spoon over sauce. Sprinkle with lemon zest.