Cheese Tortellini With Walnut Pesto

This is one of those dishes I think everyone should have in their repertoire.  It is fast, easy, yummy, inexpensive and can be made with ingredients that you can always have on  hand.  (the parsley too if you have an herb garden)  The frozen tortellini I use takes about 4 minutes to cook and the sauce is not cooked so it is done before the water even begins to boil. I think it could be a little prettier but of course, my husband disagrees with me.  It is one of his favorites, but we all like it a lot. As always, a salad will complete the meal and prevent you from making it to a high calorie meal. I believe it was another recipe I got from a Food & Wine magazine.
Cheese Tortellini With Walnut Pesto 
   1 c  walnuts
    1/3 c  lightly packed flat-leaf
           -parsley with
           -thick stems removed
      2 ea garlic,smashed
      3 T  grated Parmesan cheese,plus
           -more for serving
    1/2 c  olive oil
    1/2 t  salt
    1/4 t  fresh-ground black pepper
      1 lb fresh or frozen cheese
           -tortellini
      1 T  butter
In a food processor or blender, pulse the walnuts, parsley, garlic,
Parmesan, oil, salt, and pepper to a coarse puree.
In a large pot of boiling, salted water, cook the tortellini until just
done, about 4 minutes for fresh and 12 minutes for frozen. Reserve 1/2
cup of the pasta water. Drain the tortellini. Toss with 1/4 cup of the
reserved pasta water, the walnut pesto, and the butter. If the pasta
seems dry, add more of the reserved pasta water. Sprinkle with
additional Parmesan and pass more at the table.

Notes
Fresh, Frozen, and Dried Tortellini We recommend fresh tortellini,
which are sold in the refrigerator section of most supermarkets. Frozen
are a close second and great to have on hand. Both of these are better
than dried.