Cook the pasta in plenty of boiling salted water. In the meanwhile, place the softened (at room temperature) butter in a bowl fold it in with a whisk until foamy and soft. Next, finely chop the tuna, well drained from its oil, the desalted sardine fillets: once finely chopped whisk it with the butter and add the mascarpone, 1 tbsp of white wine and a smudge of oregano. Complete the sauce with a pinch of salt and a generous grind of pepper. Once the pasta is ready, drain it and toss it into the bowl with a couple of spoonfuls of its cooking water. Mix well and serve immediately.