Cook your ravioli as per the package instructions, in salted water.
In a small pan, toast your walnuts, constantly stirring, on medium heat. Don't walk away, they burn easily. Should take a minute or two.
Add the butter to the pan and melt. Then stir in the sage and nutmeg. Cook this sauce on low, for 3-4 minutes until butter has adopted the flavor from the sage (constantly stirring).
Divide the sauce amongst your cooked pasta and top with some grated pecorino cheese.