Cast iron bacon mac and cheese with harissa cheese sauce

Boil a pot of water with a handful of salt and cook the shells 7 minutes, short of the box time, since they finish in the oven.

Melt the fat, add the flour and cook to a wet-sand roux.

Pour in the milk, whisk well and cook on medium heat until it thickens to a heavy-cream texture that coats the sides of the pan.

Melt in the smoked cheddar and Colby Jack to a drippy consistency.

Season with harissa paste a spoonful at a time, salt and pepper, tasting until right.

Mix the pasta into the sauce; it should look almost too soupy, as the oven absorbs the extra liquid.

Put the mac and cheese in the cast iron over the solidified bacon grease, spread on the extra cheese and the topping evenly, and add a quartered serrano.

Pulse the bacon, one serrano and the breadcrumbs into a crumbly topping.

Bake at 450 for 10 minutes until the top is crisp.