Baked Mac & Cheese

Method

1. grate5 min
   cold cheese, coarse holes
   cheddar + gruyère by hand — pre-shredded cheese is dusted with starch or cellulose to keep it loose in the bag, and that coating is exactly what turns the sauce gritty. Grate it cold, then let it sit out while you build the sauce so it melts faster and needs less heat.
2. boil6 min
   hard boil, heavily salted water
   macaroni, pulled two minutes short of the box time so it still resists the tooth — it will drink sauce for 25 minutes in the oven, and pasta cooked to al dente in the pot arrives at the table as paste. Drain, do not rinse.
3. mix3 min
   medium heat
   butter melted + flour, whisked constantly until it smells faintly of biscuit and stops looking wet. Undercooked roux tastes like raw flour paste all the way through the finished dish; cook it past blond and it browns, loses thickening power, and muddies the color.
4. whisk7 min
   medium, at a bare simmer
   + warm milk in three additions, each whisked completely smooth before the next goes in. Adding it all at once makes lumps because the flour hydrates in clumps rather than dispersing. Simmer until it coats the back of a spoon — thinner than you want, since the pasta and the cheese both stiffen it.
5. mix4 min
   OFF the heat
   + grated cheddar + gruyère + dry mustard + salt + black pepper + nutmeg, a handful of cheese at a time. Off the heat is not optional: above roughly 180°F the casein proteins contract and squeeze out their fat, and the sauce splits into oily beads with a stringy mass in the middle. The mustard is not for mustard flavor — it sharpens the perception of the cheddar.
6. fold2 min
   drained macaroni + cheese sauce, until every piece is coated, then scrape into a buttered baking dish about 2 inches deep. Level it — high corners scorch before the middle heats.
7. top2 min
   breadcrumbs tossed with melted butter (+ paprika), scattered evenly over the surface. Dry crumbs left unbuttered stay chalky and pale; the fat is what lets them brown.
8. bake25 min
   375°F, uncovered, upper third
   until the edges bubble and the crumb is deep gold. Uncovered and high in the oven so moisture escapes and the top crisps — covered, it steams and the crust never forms.
9. rest10 min
   out of the oven
   before cutting. Straight from the oven the sauce is loose and runs off the spoon; ten minutes lets the starch released by the pasta finish setting so a serving holds its shape on the plate.