Ingredients
Equipment
Method
- Blanch the cauliflower: Bring a large pot of generously salted water to a rolling boil. Add the cauliflower florets and blanch for 4 to 5 minutes, until just tender with a distinct bite. While they cook, fill a large bowl with ice water.
- Shock in the ice bath: Drain the florets and plunge them straight into the ice water. Leave for 2 minutes to stop the cooking completely, then drain very well and pat dry with a clean kitchen towel.
- Make the roux: In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook, whisking constantly, for 1 to 2 minutes until faintly nutty. Whisk in the mustard powder until evenly combined.
- Build the sauce: Gradually pour in the warm milk, whisking constantly. Bring to a gentle simmer and cook 4 to 5 minutes, stirring, until the sauce thickly coats the back of a spoon. Season with the cayenne, salt, and plenty of black pepper.
- Melt in half the cheese: Take the pan off the heat. Add half of the combined shredded cheeses (about 1 1/2 cups) and stir until completely melted and glossy. Taste and adjust the seasoning.
- Assemble and top: Heat the oven to 400°F. Arrange the dry florets in the baking dish, pour over the cheese sauce, and toss gently to coat. Toss the breadcrumbs and thyme with the remaining 1 1/2 cups of cheese and scatter evenly over the top.
- Bake until golden: Bake 15 to 20 minutes, until deeply golden and bubbling at the edges. Rest 5 minutes before serving.
Notes
Cheese substitution note: Lancashire and Cheshire cheeses are hard to find in the US. Monterey Jack faithfully replaces Lancashire's milky crumble, and sharp white Cheddar or Colby replaces Cheshire's mellow saltiness. Grate the cheese yourself — pre-shredded cheese contains anti-caking starch that can make the sauce grainy.
Make-ahead note: Assemble through the topping step up to 24 hours ahead, cover, and refrigerate; add 10 to 15 minutes to the bake time. For the crispiest top, scatter the breadcrumb mixture over just before baking. Freezes well for up to 3 months; thaw overnight and reheat covered at 350°F, then uncovered to re-crisp.
