Melt the butter in a pan over medium heat but make sure it does not bubble or brown. Add the prosciutto cut into thin strips. Do not cook the prosciutto, merely leave it in the pan until it becomes warm.
When the prosciutto is warm, remove it from the heat. In a large pot of lightly salted boiling water cook the pasta for the time indicated on the package. Drain the pasta and add it to the pan with the butter and the prosciutto, add the grated Parmigiano Reggiano, stir and serve.