Cheese Sauce Melt the butter in a medium-size saucepan over medium heat. Add the flour and whisk to combine and create a roux. Add the milk a little at a time, whisking and fully incorporating after each addition. Cook the roux while stirring constantly for 4-5 minutes until it is blonde in colour and smells nutty. Remove the roux from the stove and add the cheese to the pot. Let the cheese settle in the hot roux for a minute to start melting then whisk to combine. Macaroni & Topping Preheat the oven to 200 °C. Add a pot of salted water to the stove and bring up to a boil. Add the dried macaroni. Boil the macaroni for 2 minutes less than the recommended cooking time on the packaging, as the pasta will finish cooking in the oven as it bakes. Drain the pasta reserving 1 cup (250 ml) of the pasta water. Add the pasta to the cheese sauce and mix to combine. Add a little of the pasta water to thin the sauce to the desired consistency. Add more if necessary. Transfer the macaroni to an oven dish and sprinkle a handful of grated cheese on top. Lay the frozen fish fingers evenly on the top of the macaroni and pop it into the oven. Bake for 20 minutes until the fish fingers are golden and crunchy. Remove the dish from the oven and top with grated Parmesan and chopped chives and serve.