2) In another large pot, melt the butter over medium-high heat. Whisk in the flour and continue whisking until it deepens in colour and releases a light toasted aroma, about 1 minute.
3) Whisk in the Thai red curry paste and when fully combined, pour in the milk and cream (or all milk, if using). Bring to a boil, whisking constantly, and then turn down to a simmer. Simmer until the mixture thickens, whisking occasionally, about 5 minutes.
4) Off heat, whisk in the cheeses and stir until melted. Add the pasta and toss to combine.
5) Turn your grill on.
6) For the crumb topping, toss the panko with the melted butter and season with salt and pepper.
7) To assemble, pour the mac 'n' cheese into an oven-safe casserole dish, sprinkle with the breadcrumb mixture and put under the oven grill until browned, about 1 minute.