Melt the butter in a saucepan over medium heat, as soon as it has melted, add the flour and stir for a couple of minutes, until it starts to smell nice. Add the milk, bit by bit, stirring thoroughly every time to make sure it’s fully mixed in and smooth.
Bring to the boil while stirring often, then stir through the cheese. Add some salt, if it needs it. You can also add black pepper or other spices now (see variations below).
Keep the sauce warm while you cook your pasta. In the last minute of cooking the pasta, optionally add greens to the pasta and stir them through to wilt them. Drain the pasta and greens.
Once the pasta is cooked, put the cheesy sauce back on the heat, add the drained pasta and greens and stir. When the sauce is bubbling, serve, with some fermented vegetables on the side and some extra grated cheese on top.
