I got this from my pasta cookbook, almost any kind of nut will work in this but walnuts are the one from the recipe, plus I made this with them and it was soooo good! I used an extra 4 TB olive oil instead of butter, but I'm posting it as is from the cookbook. I used jarred parmesan for convenience. This so FAST and easy, you can make this right when the ravioli is cooking, after it's done cooking, or make it ahead of time. This matches up the best with spinach ravioli and squash ravioli.