Cook the pasta: Boil the pasta in salted water until it’s about 80% cooked, a couple of minutes short of the package time. Rinse under cold water to stop the cooking, then drain well.
Preheat the oven to 180C/350F.
Mac and Cheese sauce: In a large pot over medium heat, melt the butter. Add the chopped kimchi and sauté until slightly golden and fragrant. Add the gochujang and doenjang and stir for 1 to 2 minutes to toast them and deepen their flavour.
Stir in the flour and cook for about 2 minutes to cook out the raw flour taste. Slowly pour in the milk and cream while whisking constantly until smooth and creamy. Add the parmesan, cheddar and mozzarella and stir until fully melted. Taste and season. If it’s too salty, stir in a splash more cream.
Combine: Add the cooked pasta to the sauce and stir until every piece is coated.
Bake: Transfer to a baking dish and top with the remaining parmesan. Bake for 20 to 30 minutes, until the cheese is melted, bubbling and golden brown.
Rest: Let it cool for 5 to 10 minutes before serving so the sauce can thicken and cling to the pasta.