Blanch peas in salted boiling water for a couple of minutes (more if fresh) and drain. In a non-sticking frying pan melt the butter; add ham, peas, sage, and cook for a few minutes until ham is lightly crispy. Season with salt and pepper to taste.
In the meantime, cook the Tortelloni according to package instructions and drain, reserving ½ cup of the pasta cooking water. Add Tortelloni to the pan and stir gently, adding pasta water a little at a time if you need to loosen the sauce.
Serve with grated Parmigiano Reggiano cheese alongside.