Preheat oven to 375 degrees.
Place macaroni, ham and veggies in an ovenproof dish. (I mixed everything first)
Sprinkle the olive oil evenly.
To make the cheese sauce, melt butter in a saucepan.
Stir in the flour and cook for 1 minute and keep stirring.
Reduce heat and gradually stir in the milk to a smooth sauce.
Bring to a boil, stirring and cook for another 2 minutes.
Add the mustard and half the cheese.
Season to taste with salt & pepper.
Spoon the sauce over the pasta mixture.
Sprinkle the rest of the cheese (and parsley) on top.
Bake in the oven until golden and bubbly for about 20 minutes.
Turn the temperature up briefly for quicker golden top.