Put the bay leaves, leek and milk in a
pan, and gently heat until steaming but
just below boiling point. Take off the heat
and set aside to infuse for 1 hr.
Drain the milk and discard the leek
and bay. Wipe out the pan, then add the
butter, flour and mustard powder. Heat,
stirring, until the butter has melted, then
cook to a paste for 1 min. Splash in some
milk gradually and stir until smooth and
completely incorporated. Add the rest
of the milk, a little at a time at first, then
gradually add more as the mixture gets
saucy. (If you get any lumps, give it a
vigorous whisk to remove.) Heat, stirring
all the time and scraping the bottom
of the pan so it doesn’t catch, until the
sauce is bubbling and nicely thickened.
Remove from the heat and stir in
200g of the cheddar and 25g of the
Parmesan. Season really well –
keep tasting as it will need a
generous amount of salt.
Cook the macaroni following
pack instructions, until it is almost
tender but still has a bit of chew to it.
Drain well, then stir into the cheese
sauce with three-quarters of the spring
onions. Scrape into a large ovenproof
dish or several individual ones.
Scatter the remaining cheddar over
the macaroni, then alternate between
draping over pancetta slices (bunching
them up a bit) and scattering with the
bread cubes and remaining spring
onions. (If you keep swapping between
ingredients you’ll get a nice mix of
everything on the top.) Sprinkle with the
remaining Parmesan and add a very little
drizzle of oil – holding your thumb over
the bottle so just a trickle comes out. Can now be cooled, covered and
chilled for up to 1 day, or frozen
for up to 1 month.
Heat oven to 180C/160C fan/gas 4.
Bake for 40 mins until bubbling, and
crunchy and golden on top (if using
individual dishes, check after 30 mins).