Step 1
Beat butter sugar and vanilla in bowl of a heavy-duty stand mixer* fitted with a paddle attachment on low speed just until blended and creamy 3 to 5 minutes. With mixer running on low speed gradually add flour and cocoa and beat until dough comes together about 1 minute stopping to scrape down sides of bowl as needed. Beat in 2 cups chocolate chips on low speed until just combined.
Step 2
Divide dough in half and roll each half into a compact 2-inch-thick log (about 8 inches long). Wrap each log in parchment paper or plastic wrap and freeze just until firm (but not frozen solid) about 25 minutes.
Step 3
Preheat oven to 350 degrees F. Line 2 large rimmed baking sheets with parchment paper.
Step 4
Remove cookie dough logs from freezer and unwrap. Using a sharp serrated knife and a sawing motion cut cookie dough into 1/2-inch-thick rounds. If rounds crumble slightly press dough back together. Place rounds on prepared baking sheets spacing cookies about 2 inches apart.
Step 5
Bake 1 sheet at a time in preheated oven until firm 15 to 18 minutes. Let cool completely on baking sheets about 20 minutes.
Step 6
To decorate place one 12-ounce package Ghirardelli semi-sweet chocolate chips in a medium microwaveable bowl. Microwave on HIGH until chocolate is melted and smooth about 1 minute stirring at 30-second intervals. Dip each cookie halfway into melted chocolate and place on parchment paper-lined baking sheets.
Step 7
Refrigerate until chocolate has set about 15 minutes.