Cook the pasta in a large quantity of water as per the instructions on the packet. Remove the rind from the Reblochon.
Make a béchamel sauce: in a saucepan, melt the butter, and when melted add the flour, stir with a wooden spatula until it dries and takes on a light beige colour. Add the cold milk and cook without boiling, while stirring with the spatula until the mixture thickens.
Add the 1/4 Reblochon and let it melt into the sauce. Preheat the oven to 180°C (th.6). Cut the chorizo into slices and remove the skin.
Prepare a baking dish large enough to hold the pasta and the chorizo. Mix the pasta, chorizo, béchamel sauce, season and pour into the baking dish. Chop the rest of the Reblochon (the other 1/4) into slivers and use it to cover the pasta.
Bake for about fifteen minutes, until the bake starts to turn golden.