I've shared these cookies before but it was years ago and I think they deserve a second go-round. I almost always make a double batch (the recipe below is the double batch - you can cut it in half easily) because the dough freezes well and I think cleaning up a bowl of chocolate dough is such a pain that you should really maximize the number of cookies you get out of it.
The only changes I've made are to increase the salt (I still think it might be a little low but I'm reluctant to advise you to increase it further without testing it myself - I do sprinkle a couple flakes of sea salt on each cookie as well) and swap out the white chocolate chips for peanut butter chips from Trader Joe's. These are great with white chocolate but I think the peanut butter is even better.
Chocolate cookies (makes a TON of cookies but the dough freezes well, can be cut in half if you're not ready to commit - original recipe here)
2 pounds bittersweet or semisweet chocolate, chopped (I use chocolate chips)
1/2 cup unsalted butter
1 cup all purpose flour
1 teaspoon. baking powder
1 teaspoon salt
1 1/2 cups brown sugar
1 1/2 cups granulated sugar
20 oz. peanut butter chips (can substitute white chocolate chips)
4 cups chopped walnuts
Flaky salt for finishing
:: Melt the chocolate and butter over hot water. You don't have to have a double boiler. I just take one of my aluminum mixing bowls and rest it over a pot with boiling water in it and it works well enough. If you have a microwave, use it. Just stir every 30 seconds or so. Once the chocolate is melted set it aside and let is cool slightly.
:: Whisk together the flour, baking powder and salt in a small bowl.
:: Beat the eggs with the sugars until light and stir in the melted chocolate. Add the flour mixture, peanut butter chips and nuts. Refrigerate the dough for at least a couple hours (it will be way too sticky until it cools down).
:: OPTION 1 - Shape the dough into rolls, like refrigerator cookies. This is a little tricky. Keep your hands well floured and don't worry too much about the mess. You'll have to experiment to see how thick you want the logs to be. Wrap with saran wrap, and then wrap with aluminum foil and put in a ziploc freezer bag if you plan to store them for more than a few days. Wrapped up well, they will last for at least 2 months in the freezer (probably longer, but they usually get eaten quickly). Let them sit in the freezer for at least a day before you try to cut them - it works better if they are really frozen solid.
:: OPTION 2 - Scoop and bake. This is what I've been doing lately and it works perfectly well. I think the extra large cookies bake better but the smaller ones are more socially acceptable. This last time I made both sizes, using a 1/3 cup cookie scoop (#12) for the enormous cookies and a much more modest one (#50) for the smaller ones. The dough is thick so it can be hard on your cookie scoops. I was careful to clean them out with a small spatula after every few cookies. You can freeze the scoops too, as I describe here.
:: Preheat the oven to 350 degrees F. Line cookie sheets with parchment paper or Silpat - they will absolutely stick to the sheet if you don't. If you made rolls, slice the cookies 1/2 inch thick. Sprinkle each cookie with a few flakes of sea salt.
:: Bake until they lose their sheen. It's hard to tell when these are done but when the top seems dry and is no longer glossy you're usually good to go. Let them cool fully on the cookie sheet. They'll fall apart if you try to move them while they're still warm. They should be moist and chewy inside once cooled.
Baking time estimates:
Sliced cookies (1/2" thick) - 10 - 12 minutes
Scooped cookies (small #50 scoop) - 10 - 15 minutes
Scooped cookies (large #12 scoop) - 15 - 25 minutes (check every 5 min)