Broccoli and ham pasta bake

• 1100 g water
• 10 g vegetable oil
• 1 tsp sea salt
• 400 g penne pasta
• 300 g broccoli, broken into florets

Cheese sauce

• 100 g Gruyère cheese, cut in pieces (2 cm - see Tips)
• 700 g full cream milk
• 70 g salted butter, cut into cubes
• 70 g plain flour
• 1 tsp Dijon mustard
• 1 tsp sea salt
• ½ tsp ground black pepper
• 150 g smoked ham, cut into pieces (approx. 2 cm - see Tips)