1.Melt butter in medium frying pan, add cream; bring to the boil then reduce heat. Simmer, uncovered, about 5 minutes or until mixture reduces by half.
2.Remove pan from heat; add cheeses gradually, stirring, until sauce is almost smooth.
3.Serve sauce with gnocchi or pasta, if you like.
Serve this sauce immediately on 500g freshly cooked rigatoni or other short pasta to serve 4 as a main course or 6 as a starter. Use other cheeses if the ones here are unavailable. Gruyère, provolone, raclette, vintage cheddar or a mild blue are all great possibilities.