I have been baking for YEARS, close to 30 years if I count, and I thought I knew a thing or two about chocolate chip cookies. After much trial and error I have narrowed down my repertoire to two or three consistent recipes that yield perfectly acceptable results. All of these recipes are different versions of the same theme, a blend of butter (I despise margarine; no flavour and greasy), brown and white sugars, pure vanilla extract, pure bittersweet chocolate chips, optional nuts, etc. And everyone makes chocolate chip cookies, so I was not prepared to be blown away by yet another rendition. Then I met this recipe on the excellent website/food journal 101cookbooks.com. You may be wondering what could possibly be so great about it. Its excellence is all in the details and the perfect balance of the proportions. Heidi Swanson, the creator of 101cookbooks.com, describes these extraordinary cookies, which she found in the book The Great Book of Chocolate by David Lebovitz: "A high chip to dough ratio guarantees lots of chocolate in every bite, and the walnuts add crunch, density, and a delicious flavor to the overall mix. If you like a thin and crispy chocolate chip cookie, pass on this one. If you like them substantial, big, rich, chunky, gooey, and decadent.......this recipe is all yours". Let me add my own 2-cents, after just eating one on my coffee break: the brown sugar gives the cookie a butterscotch-y chewiness, offset by the toasty crunch of walnuts and the deep bittersweet hits of chocolate. All the flavours meld together in a perfect marriage.
Enough said; here is the recipe for the best chocolate chip cookie I have ever eaten, and I have eaten a few 
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THE GREATEST CHOCOLATE CHIP COOKIE RECIPE
1/2 cup granulated sugar; 1/2 cup firmly packed light brown sugar; 8 tablespoons (1 stick) unsalted butter cut into 1/2" pieces; 1 large egg; 1 teaspoon pure vanilla extract; 1/2 teaspoon baking soda; 1+1/4 cup all-purpose flour; 1/4 teaspoon salt; 1+1/2 cups semisweet chocolate chips; 1 cup walnuts or pecans, toasted and chopped.
Beat the sugars and butter together until smooth. Mix in the egg and vanilla. Stir together the flour, salt and baking soda then mix them into the batter. Mix in the chocolate chips and nuts. Chill dough overnight or for at least 3 hours.
Adjust the oven rack to the top 1/3 of the oven and preheat to 300 F. Line a large baking sheet with parchment paper.
Scoop the cookie dough into 2-tablespoon balls and place balls 4 inches apart on the baking sheet. Flatten each ball very slightly with the palm of your hand.
Bake for 18 minutes, or until pale golden brown. Do not overbake if you want a good, chewy texture. Remove from the oven and cool on a wire rack.
Store at room temperature in an airtight container for up to 3 days.
Make about 20 cookies.
Of course, there are other wonderful chocolate chip cookie recipes in the world and in our library collection. For a little variety, try these books:
The essential chocolate chip cookbook : recipes from the classic cookie to mocha chip meringue cake / by Klivans, Elinor.
Maida Heatter's book of great chocolate desserts / by Heatter, Maida.
Martha Stewart's cookies : the very best treats to bake and to share / by Stewart, Martha.