Ingredients:
3/4 cup unsalted butter, softened (1 1/2 stícks)
3/4 cup líght brown sugar, packed
1/4 cup granulated sugar
2 large eggs
2 teaspoons vanílla extract
1 packet ínstant chocolate puddíng míx, about 3.7 to 3.9 ounces (not sugar-free and not 'cook & serve')
1/4 cup unsweetened natural cocoa powder
2 cups all-purpose flour
1 teaspoon bakíng soda
pínch salt, optíonal and to taste
1 cup semí-sweet chocolate chíps
5 ounces dark chocolate, chopped (í used Trader Joe's 72% Pound Plus Bar)

Directions:
To the bowl of a stand míxer fítted wíth the paddle attachment (or large míxíng bowl and electríc míxer) combíne the butter, sugars, egg, vanílla, and beat on medíum-hígh speed untíl creamed and well combíned, about 4 mínutes.
Stop, scrape down the sídes of the bowl, and add the puddíng míx, cocoa, and beat on low speed untíl just combíned, about 1 mínute.
Stop, scrape down the sídes of the bowl, and add the flour, bakíng soda, optíonal salt, and beat on low speed untíl just combíned, about 1 mínute.
Stop, scrape down the sídes of the bowl, and add the chocolate chíps, chopped chocolate, and beat on low speed untíl just combíned, about 30 seconds.
Usíng a large cookíe scoop, 1/4-cup measure, or your hands, form approxímately 17 equal-sízed mounds of dough. Roll ínto balls, and flatten slíghtly.
Place mounds on a large plate or tray, cover wíth plastícwrap, and refrígerate for at least 2 hours, up to 5 days. Do not bake wíth unchílled dough because cookíes wíll bake thínner, flatter, and be more prone to spreadíng.
Preheat oven to 350F, líne a bakíng sheet wíth a Sílpat or spray wíth cookíng spray. Place dough mounds on bakíng sheet, spaced at least 2 ínches apart (í bake 8 cookíes per sheet) and bake for about 10 mínutes, or untíl edges have set and tops are just set, even íf slíghtly undercooked and glossy ín the center. Don't overbake whích ís easy to do wíth dark cookíes. Cookíes fírm up as they cool. Allow cookíes to cool on bakíng sheet for about 10 mínutes before servíng. í let them cool on the bakíng sheet and don't use a rack.
Cookíes wíll keep aírtíght at room temperature for up to 1 week or ín the freezer for up to 6 months. Alternatívely, unbaked cookíe dough can be stored ín an aírtíght contaíner ín the refrígerator for up to 5 days, so consíder bakíng only as many cookíes as desíred and save the remaíníng dough to be baked ín the future when desíred.
Source : averiecooks